1 00:00:05,500 --> 00:00:10,180 Thank you very much for inviting me. It's an absolute pleasure to be here. 2 00:00:10,180 --> 00:00:15,380 I should put my microphone on. Good. 3 00:00:15,380 --> 00:00:25,280 And thank you to Michael's family for making sure that Michael's wishes were put into practise. 4 00:00:25,280 --> 00:00:40,280 I'm going to try and do a few demonstrations today, and I'm it's very difficult when trying to sum up the impact of the work please have. 5 00:00:40,280 --> 00:00:44,900 And so I apologise now for the things I leave out. 6 00:00:44,900 --> 00:00:48,170 It's just not possible to do everything. 7 00:00:48,170 --> 00:00:59,020 So I've tried just to pick a few things that will highlight what has happened and what is happening and what is going to happen. 8 00:00:59,020 --> 00:01:06,460 And so I thought we ought to start with a picture of rubbish. 9 00:01:06,460 --> 00:01:14,830 I think this dates back to when he was made a fellow of St John's in 1947, 10 00:01:14,830 --> 00:01:22,390 and he noticed that Brevet first came up to Oxford in 1934 as an undergraduate, 11 00:01:22,390 --> 00:01:34,360 that he fell in 1939 and then spent a lot of time working here on the Admiralty on the development of radar. 12 00:01:34,360 --> 00:01:42,120 He told me that he used to enjoy goading Nicholas Curtin. 13 00:01:42,120 --> 00:01:46,020 Because he was allowed to work on radar. 14 00:01:46,020 --> 00:01:55,590 And Nicholas wasn't. And so there was apparently a little rope on to stands across the corridor, 15 00:01:55,590 --> 00:02:03,180 and Nicolas would be shouting for privates and privates would always pretend not to hear. 16 00:02:03,180 --> 00:02:09,360 And one thing I do remember about Brevis is he had a very, very good sense of humour. 17 00:02:09,360 --> 00:02:16,410 And when I was a graduate student, Travis used to pop into the lab to come and fetch us for coffee. 18 00:02:16,410 --> 00:02:22,550 And Robert's right. I will talk a little bit about Diamond later on Brevis, actually. 19 00:02:22,550 --> 00:02:37,520 I sat on the De Beers Diamond Research Committee, and this committee has been funding research at UK universities for 70 years this year. 20 00:02:37,520 --> 00:02:43,040 And Bobby Bowman was one of the first people to be funded in Oxford, 21 00:02:43,040 --> 00:02:52,010 and there are some wonderful minutes of the early meetings of the Diamond Conference and the be unguaranteed of me to tell you who it was. 22 00:02:52,010 --> 00:02:59,000 But Professor Andrew Lang from the University of Bristol was giving a talk in Oxford at the Diamond Conference, 23 00:02:59,000 --> 00:03:03,350 and hopefully I won't go on as long as Andrew did. 24 00:03:03,350 --> 00:03:10,310 And it was described as micrograph after micrograph after micrograph, and Brevis wanted his lunch, 25 00:03:10,310 --> 00:03:16,550 apparently so as Chest stood up and stopped, Andrew and Andrew said It was quite all right. 26 00:03:16,550 --> 00:03:26,070 And people come and look at the micrographs during lunchtime and breakfast just turned to the audience and said, Don't all rush at once. 27 00:03:26,070 --> 00:03:33,080 So, yeah, I remember Brevis with considerable affection, 28 00:03:33,080 --> 00:03:44,840 and then I do remember him coming into the lab and fiddling with the spectrometer and it taking us about a month to get it to work again puts him at. 29 00:03:44,840 --> 00:03:53,710 John Gregg lent me these nice pictures. I really like the one from Michael Baker and Brabus together. 30 00:03:53,710 --> 00:03:58,690 And I remember them both like this often in deep conversation about something 31 00:03:58,690 --> 00:04:05,290 that I didn't understand and I needed explaining to me at great length later on. 32 00:04:05,290 --> 00:04:12,970 And I thought it worth putting this photograph up, seeing as we're here in Oxford today, 33 00:04:12,970 --> 00:04:28,270 just looking at several of the people who really made a significant impact to the development of EPA. 34 00:04:28,270 --> 00:04:33,010 And sadly, many of them not with us anymore. 35 00:04:33,010 --> 00:04:45,080 But Bill Hayes, who I believe is immortal, is of course looking at exactly the same at the end. 36 00:04:45,080 --> 00:04:52,050 So what is electron paramagnetic resonance? 37 00:04:52,050 --> 00:05:06,600 When you ask yourself a question like that, it's often very difficult to answer succinctly and really it is a field that is used to study stuff. 38 00:05:06,600 --> 00:05:13,350 Anything you like as long as there are unpaired electrons. 39 00:05:13,350 --> 00:05:18,540 So radicals transition, metal ions, defects in materials. 40 00:05:18,540 --> 00:05:27,390 These all can have electrons that are not paired away, so there is some net spend, some net magnetism, 41 00:05:27,390 --> 00:05:42,000 so many processes that keep us alive and photosynthesis oxidation reactions are governed by radicals and catalysis polymerisation. 42 00:05:42,000 --> 00:05:55,990 So EPR finds applications in many, many disciplines not just physics, chemistry, biology, materials science, medicine and many, many more. 43 00:05:55,990 --> 00:06:03,430 And really, the basic concepts of EPR are very similar to those of nuclear magnetic resonance. 44 00:06:03,430 --> 00:06:09,900 But it's just the electron spins that we're dealing with rather than the nuclei. 45 00:06:09,900 --> 00:06:18,780 And. The field was born very much because of the technological advancement that came about 46 00:06:18,780 --> 00:06:26,310 through the development of radar in terms of making the microwave sources and detectors. 47 00:06:26,310 --> 00:06:42,750 So in a sense, Brabus was in the vanguard of the first revolution, but the second revolution in electron resonance is really being brought about by. 48 00:06:42,750 --> 00:06:54,460 Mobile phone. And high speed electronics, which enables us to do many clever things with microwaves. 49 00:06:54,460 --> 00:07:04,280 So that is a great parallel to what is happening today, to what happened back 50 plus years ago. 50 00:07:04,280 --> 00:07:10,460 So I've dug out some pictures of what was happening 50 plus years ago. 51 00:07:10,460 --> 00:07:22,730 The picture on the left is actually from Warwick and this is of the era where companies such as Decker made scientific equipment. 52 00:07:22,730 --> 00:07:31,070 So is the X1 EPR spectrometer installed at Warwick in nineteen sixty seven? 53 00:07:31,070 --> 00:07:39,510 So that's only two years after the university was founded. And MJ Smith is running it. 54 00:07:39,510 --> 00:07:47,390 He came from the Admiralty to work where he had been working on radar. 55 00:07:47,390 --> 00:07:55,790 So this is a picture from the Clarendon. We're not quite sure when, but it's the early 1960s. 56 00:07:55,790 --> 00:08:00,800 Michael's, a very modest and shy man, didn't like his picture being taken, 57 00:08:00,800 --> 00:08:05,630 so it was rapidly advancing on the camera, but didn't quite make it home in time. 58 00:08:05,630 --> 00:08:15,410 This is downstairs room 00:42 and shows some of the Apple hardware in the background. 59 00:08:15,410 --> 00:08:28,310 This picture, again, I can't quite date properly, but is some time from the early nineteen eighties, judging by Andy Sutton's haircut. 60 00:08:28,310 --> 00:08:35,370 And Michael had several sayings and one of which I liked a lot, which was in the. 61 00:08:35,370 --> 00:08:43,380 Time before health and safety was invented, so you can see and the pouring in the liquid nitrogen without any safety goggles. 62 00:08:43,380 --> 00:08:54,630 Michael watching with the blue laser, without any safety goggles, no interlocks and I should point out I recognise this. 63 00:08:54,630 --> 00:09:02,040 This is one of the high voltage climbs from power supplies, because when I came in the. 64 00:09:02,040 --> 00:09:06,030 And in the 1980s, do my thing that was still there. 65 00:09:06,030 --> 00:09:13,410 And in the true spirit of health and safety in Clarendon, I was electrocuted on my first day at work. 66 00:09:13,410 --> 00:09:18,450 But it was only a thousand votes. And as Michael pointed out to me. 67 00:09:18,450 --> 00:09:32,700 And. This picture was given to me by David Collison, who is at the University of Manchester, and I put this up. 68 00:09:32,700 --> 00:09:40,770 I'm old enough just to remember chart recorders, so this is how the EPR spectra were recorded. 69 00:09:40,770 --> 00:09:46,350 You had your clockwork motor, sometimes an electric motor, hold your chart paper through. 70 00:09:46,350 --> 00:09:54,480 You got halfway through recording your date of your pen run out. Yeah, but you can see this is data from 1968. 71 00:09:54,480 --> 00:10:01,470 It's cobalt in some compound and you could see the cobalt have a fine structure which will come to you later. 72 00:10:01,470 --> 00:10:09,480 And the technology is now coming back across the Atlantic from Varian in the US, 73 00:10:09,480 --> 00:10:18,210 and all of a sudden spectrometers could be bought rather than built component by component. 74 00:10:18,210 --> 00:10:24,050 And this is where we are pretty much today. 75 00:10:24,050 --> 00:10:34,400 This is just a selection of EPA spectrometers with six Tesla magnets running at nine to four gigahertz, 76 00:10:34,400 --> 00:10:40,020 running at 10 gigahertz and even an EPR imaging machine. 77 00:10:40,020 --> 00:10:49,730 I put this up just to point out the international EPR society has a thousand members give or take. 78 00:10:49,730 --> 00:10:57,080 The Royal Society of Chemistry is our great European Federation of EPR groups very 79 00:10:57,080 --> 00:11:02,630 successful run meetings with several hundred delegates annually attending them. 80 00:11:02,630 --> 00:11:15,200 So this really is a legacy of rubbish as work, Michael's work and others in the Clarendon who had developed the field of EPR. 81 00:11:15,200 --> 00:11:22,000 And I just wanted to show here is a tabletop EPR spectrometer. 82 00:11:22,000 --> 00:11:27,940 And so the technology has changed now so we can run it in teaching labs. 83 00:11:27,940 --> 00:11:33,230 And. I'm going to try and be very brave. 84 00:11:33,230 --> 00:11:44,950 So I have a sample. Yeah, which is plasticine now, which I got off a four year old yesterday. 85 00:11:44,950 --> 00:11:54,700 And if the technology works, I can pop it in the spectrometer and press June. 86 00:11:54,700 --> 00:12:00,430 Some of the old timers will realise that now we have dispensed with postgraduate students. 87 00:12:00,430 --> 00:12:07,870 If the spectrometer can tune itself at the spectrometer, the graduate students can go and do something more interesting. 88 00:12:07,870 --> 00:12:14,920 I'm greatly relieved. You can see in the top left, it's found the resonant mode of the cavity, 89 00:12:14,920 --> 00:12:23,960 and it is now going through optimising the phase of the microwave bridge to hopefully. 90 00:12:23,960 --> 00:12:32,930 They don't realise how relieved I am, because now all we have to do is to press start sweet. 91 00:12:32,930 --> 00:12:39,470 And this will take about 20 seconds. There's a little near the magnet with some sweet clothes either side of it. 92 00:12:39,470 --> 00:12:44,070 It is scanning through 600 gaps in old money. 93 00:12:44,070 --> 00:12:51,290 60 Tesla a new money to see if there are any unpaired electrons in the plasticine. 94 00:12:51,290 --> 00:13:04,630 Any defects to the paramagnetic in this material. And the relief there are now who can recognise anything about that spectrum. 95 00:13:04,630 --> 00:13:14,950 It's a power spectrum because it's plasticine and some people will spot that there is a repeating structure of six lines, 96 00:13:14,950 --> 00:13:27,620 which gives you a clue that it is actually manganese ions as an impurity, a transition metal iron impurity in the plasticine. 97 00:13:27,620 --> 00:13:35,340 The field has come a long way from building your own spectrometers. 98 00:13:35,340 --> 00:13:40,380 This little tabletop machine will do free radicals in coffee. 99 00:13:40,380 --> 00:13:48,200 It will do free radicals in orange juice. 100 00:13:48,200 --> 00:13:53,140 It has a very, very important application. 101 00:13:53,140 --> 00:14:07,480 It is used commercially to assess the quality of beer, and the brewers look for free radicals in the beer that can make it taste sour. 102 00:14:07,480 --> 00:14:13,780 Yeah, and actually EPA is used as a process control technique. 103 00:14:13,780 --> 00:14:20,480 It's also now used in some wine production as well. 104 00:14:20,480 --> 00:14:28,890 So many, many applications, and I say I apologise, I haven't got time to go through most of them. 105 00:14:28,890 --> 00:14:34,390 But EPR has a huge impact in chemistry. 106 00:14:34,390 --> 00:14:46,350 This is a subject like physics. But more complicated. 107 00:14:46,350 --> 00:14:56,360 And I would say. In the last 20 years, this is probably where EPR has made the most impact. 108 00:14:56,360 --> 00:15:02,070 But it is rapidly moving into biology and medicine. 109 00:15:02,070 --> 00:15:12,030 And it has come back into fashion, postgraduate students should never worry about a field being out of fashion. 110 00:15:12,030 --> 00:15:18,520 You should worry about a field being in fashion because all that can happen to it is it goes out of fashion. 111 00:15:18,520 --> 00:15:30,040 And I hope I'll show you towards the end of the talk in about three hours time where EPR has come back full circle to physics department. 112 00:15:30,040 --> 00:15:35,560 And I've also already mentioned that it is used in food and beverages. 113 00:15:35,560 --> 00:15:40,300 Pharmaceutical companies use it and it is used for radiation dosimetry. 114 00:15:40,300 --> 00:15:46,640 So most of the imported strawberries that you could buy at this time of year have been irradiated. 115 00:15:46,640 --> 00:15:53,930 Stop them going mouldy, and EPR is used to make sure that the dose is not too high. 116 00:15:53,930 --> 00:16:06,920 So I thought it was just worth doing. April one, I want just to go back and think about what where the field actually came from. 117 00:16:06,920 --> 00:16:13,440 So a spin is a property possessed by an electron. 118 00:16:13,440 --> 00:16:19,680 And again, it's a very difficult thing to comprehend, but sort of an election has charge. 119 00:16:19,680 --> 00:16:25,500 And if the electron is rotating, then there's a current currents produced magnetic fields. 120 00:16:25,500 --> 00:16:32,160 So you sort of expect a spin to produce an electron, sorry to produce its own magnetic field. 121 00:16:32,160 --> 00:16:39,660 And that's certainly the case. So you can treat the electrons as if they were tiny little magnets. 122 00:16:39,660 --> 00:16:48,390 So if you were to place an electron in a magnetic field, it would be in a low energy configuration. 123 00:16:48,390 --> 00:16:57,210 If the north south was aligned with the field and in the high energy configuration, if it was a. parallel to the field. 124 00:16:57,210 --> 00:17:08,740 So we have a way of applying a magnetic field and splitting the energy levels that belong to the electron spin up and spin down. 125 00:17:08,740 --> 00:17:15,550 So an electron has a spin a half, so we have to spin projection quantum numbers plus a half and minus half. 126 00:17:15,550 --> 00:17:19,990 We associate the energy levels with plus the half of minus the half. 127 00:17:19,990 --> 00:17:26,440 The Zeeman splitting now is proportional to the magnetic field, a fundamental constant. 128 00:17:26,440 --> 00:17:36,850 And gee, I've not got time to talk about Gee today, but it makes the maths more complicated because it's there for lots of things. 129 00:17:36,850 --> 00:17:44,120 But we split the energy levels and we drive. We can drive transitions between them. 130 00:17:44,120 --> 00:17:51,140 And the key thing is at accessible magnetic fields, these transitions. 131 00:17:51,140 --> 00:18:00,400 The photon energy that is required to flip from one spin state to another is in the microwave region of the spectrum. 132 00:18:00,400 --> 00:18:05,760 So somewhere between a gigahertz and maybe 100 gigahertz. 133 00:18:05,760 --> 00:18:17,550 And this magnet is actually the Valskis magnet, where he first did EPR in nineteen forty four, so that's from the Volsky Museum. 134 00:18:17,550 --> 00:18:26,330 So that dates to the time and the clarendon that EPR was being discovered. 135 00:18:26,330 --> 00:18:39,570 Now. In those days, people were talking about ensemble EPR and that we mean we've got lots of spins. 136 00:18:39,570 --> 00:18:48,210 And you can think of this if you have 200000 spins, 200000 electrons at room temperature. 137 00:18:48,210 --> 00:18:56,110 100 thousand and one. Will be spin up. 138 00:18:56,110 --> 00:19:01,190 And ninety nine thousand nine hundred ninety nine will be spent down. 139 00:19:01,190 --> 00:19:08,890 So the net excess spin up and spin down is two in 100000 roughly. 140 00:19:08,890 --> 00:19:13,450 So actually, the magnetism is very weak. Yeah. 141 00:19:13,450 --> 00:19:23,740 So in order to get a signal where we're able to detect that this microwave quantum has been observed, the microwave radiation has been absorbed. 142 00:19:23,740 --> 00:19:33,340 We're talking about having to have 10 to the 12 spins to get a signal that is big enough to see. 143 00:19:33,340 --> 00:19:42,840 And we are in a situation where these level populations can be determined by Matt Maxwell Boltzmann statistics. 144 00:19:42,840 --> 00:19:51,840 And. You would think to yourself, well, if there's a population difference between the two levels, there must be some way of maintaining it. 145 00:19:51,840 --> 00:19:59,910 And this comes back to Spain latticed relaxation. If we flip a spin from the low state to the upper state, 146 00:19:59,910 --> 00:20:09,120 it will relax back by emitting a quantum of vibrational energy, a phone phonon, the simplest way to come back. 147 00:20:09,120 --> 00:20:18,150 So really, now we have the early days of quantum physics linking through to thermodynamics. 148 00:20:18,150 --> 00:20:24,690 And in a sense, this is why the planet was the obvious place to do this because everything was 149 00:20:24,690 --> 00:20:33,740 coming together in the physics department to do exactly the sort of experiments. 150 00:20:33,740 --> 00:20:38,780 But the experiment have just described a single spin. 151 00:20:38,780 --> 00:20:46,460 Either parallel runs, parallel field dry, a transition between it gives us one absorption line, 152 00:20:46,460 --> 00:20:54,400 one single line with a resonance condition, highest use tube so we can determine Gee. 153 00:20:54,400 --> 00:21:01,330 This would be a pretty boring field if you got one line. 154 00:21:01,330 --> 00:21:13,350 There's not that much information. But fortunately, the electron is very sensitive to everything that surround it, 155 00:21:13,350 --> 00:21:21,940 and especially the interactions with the stuff that is around these unpaired electrons. 156 00:21:21,940 --> 00:21:31,330 So again, we'll just do a little tutorial here, we have an unpaired electron in a magnetic field. 157 00:21:31,330 --> 00:21:38,130 The spin generates its own magnetic field, interacts with the applied field and splits the two levels. 158 00:21:38,130 --> 00:21:43,950 The same happens for nuclei. With spin. 159 00:21:43,950 --> 00:21:49,950 Yeah. The minus sign comes about here because the charging electron is negative, 160 00:21:49,950 --> 00:21:55,500 so just to keep everything same, we have to a minus sign for the New Zealand taxi. 161 00:21:55,500 --> 00:22:03,450 But of course, the electron can see the magnetic field, but the nucleus spin generates and vice versa. 162 00:22:03,450 --> 00:22:14,340 So they coupled together one magnetic dipole sees the other magnetic dipole, and we have the so-called hyper fine interaction coupling. 163 00:22:14,340 --> 00:22:24,970 These two spins together. And the moment you do that, you say to yourself, Well, I can drive my EPR transitions, I can flip my spin. 164 00:22:24,970 --> 00:22:29,050 I'm going to leave the nuclei alone. Does anybody here who does NMR? 165 00:22:29,050 --> 00:22:34,750 I'm going to be so rude about an email later on. That's to come. But NMR is quite useful. 166 00:22:34,750 --> 00:22:39,010 Yeah. So now we have the electron cup of the nucleus. 167 00:22:39,010 --> 00:22:47,320 So we have two possible transitions. And the splitting between the two lines tells us the strength of this hypothyroid interaction. 168 00:22:47,320 --> 00:22:56,450 All of a sudden, we are getting information about the environment of the electron and what it is coupled to. 169 00:22:56,450 --> 00:23:05,480 For a technical reason, in most continuous way, he experiments the spectra is recorded as the first derivative absorption signal, 170 00:23:05,480 --> 00:23:12,630 so we have to get used to looking at lines like this derivative line shapes. 171 00:23:12,630 --> 00:23:25,710 So we now have an exam question. We have a radical yeah, and I've picked this one because it was an exam question last year at work. 172 00:23:25,710 --> 00:23:30,000 This is a small piece of graphene, if you like. 173 00:23:30,000 --> 00:23:33,660 Terminated with hydrogen. And I'm a physicist. 174 00:23:33,660 --> 00:23:39,810 Each of these little dots is where a carbon atom is on the carbon likes to form. 175 00:23:39,810 --> 00:23:44,340 Four bombs now, one, two, three four with the hydrogen. 176 00:23:44,340 --> 00:23:51,280 But if you go round this little link, you can't do it. There's one carbon atom that is going to be unhappy. 177 00:23:51,280 --> 00:24:00,580 And actually, you can't tell which of the carbon atoms is going to be because it could be any of them around the outside of the ring. 178 00:24:00,580 --> 00:24:09,810 So effectively you have an unpaired electron, a spin that is localised over the entire molecule. 179 00:24:09,810 --> 00:24:14,620 And that spin is going to interact with the things that are around it. 180 00:24:14,620 --> 00:24:21,820 Well, carbon is ninety nine percent, ninety eight point nine percent carbon, 12, no nuclear spin, 181 00:24:21,820 --> 00:24:28,540 so there's not going to be an interaction with the carbon 12, but the protons are all nuclear spin off. 182 00:24:28,540 --> 00:24:38,290 There's going to be interaction with the protons. So we have a clue as to where this rich spectral information comes from. 183 00:24:38,290 --> 00:24:48,310 And we have to remember that when we had one nuclear spin, a half cup of the electron, it split our spectrum into two. 184 00:24:48,310 --> 00:24:55,560 We had two lines. If we have an identical splitting with a second, it's been a half, 185 00:24:55,560 --> 00:25:03,090 it'll split those both into two again, so we generate a one to one pattern and we can go down the list. 186 00:25:03,090 --> 00:25:08,250 So if we have three, we get one three three one. If we have six. 187 00:25:08,250 --> 00:25:17,630 We have one six, 15, 20, 15, six one. So remember those patterns and go back to look at the spectrum. 188 00:25:17,630 --> 00:25:22,730 And look at the molecule, we have free hydrogen, if you like, 189 00:25:22,730 --> 00:25:28,820 on the corners of this molecule that are all equivalent that are coupled with d localised unpaired 190 00:25:28,820 --> 00:25:37,790 light from three regions should give us one three three one and we can see that one three three one. 191 00:25:37,790 --> 00:25:43,910 And then it's bigger one three three one one three three one as we go through the spectrum. 192 00:25:43,910 --> 00:25:53,990 So we see the coupling with these protons and then we notice we've got six equivalent protons that are effectively on the side of the triangle. 193 00:25:53,990 --> 00:25:58,400 So we have a splitting with six of hydrogen atoms, which gives us the one, six, 15, 194 00:25:58,400 --> 00:26:05,870 2015 six one, so we have one set of splitting that is split again into the one three three one. 195 00:26:05,870 --> 00:26:11,600 So actually, the spectrum is relatively straightforwardly explained. 196 00:26:11,600 --> 00:26:16,220 You'll notice that there are the occasional small line that we haven't explained. 197 00:26:16,220 --> 00:26:21,710 But, of course, that it's a one percent chance of each of these carbons is a carbon 13. 198 00:26:21,710 --> 00:26:35,440 And these are carbon 13 hydrophone satellites. I put that example up, because that is a routine application of EPA to identify a radical. 199 00:26:35,440 --> 00:26:43,420 Yeah. And that is used day in, day out around the world to dry chemistry, 200 00:26:43,420 --> 00:26:53,500 whether it's reactions of radicals in the human body or new routes to catalysis, the polymerisation. 201 00:26:53,500 --> 00:27:05,230 That's what is going on. And we've said I've said the electron is sensitive to its environment, and that's certainly true. 202 00:27:05,230 --> 00:27:15,620 And this is where it starts to get a bit complicated. This is very sensitive to its environment. 203 00:27:15,620 --> 00:27:25,250 And this is where I used to and still get terrified with the spin Hamiltonian. 204 00:27:25,250 --> 00:27:32,500 And in truth, it's the effective spin Hamiltonian, because as Michael Baker. 205 00:27:32,500 --> 00:27:37,730 Said to me. We teach. 206 00:27:37,730 --> 00:27:46,360 By the law of diminishing deception. There are so many things hidden in spin Hamiltonians. 207 00:27:46,360 --> 00:27:52,630 That it is hard to know where to start. And. 208 00:27:52,630 --> 00:28:03,360 When I was a lecturer here, I had a Ph.D. student who's worked with Michael Baker myself called Andrew Cox. 209 00:28:03,360 --> 00:28:14,380 And Andrew came into my office at about three o'clock on a Friday afternoon saying that an old man had walked into the lab. 210 00:28:14,380 --> 00:28:21,040 And wouldn't go away and was asking questions that nobody could answer. 211 00:28:21,040 --> 00:28:24,760 So I walked down to the lab and there was no man in the lab, 212 00:28:24,760 --> 00:28:31,400 and he was asking very awkward questions and would only leave the lab and have to buy him a cup of tea and a biscuit. 213 00:28:31,400 --> 00:28:39,440 And he wouldn't tell me who he was until he made me drive Hamiltonian for a specific case. 214 00:28:39,440 --> 00:28:46,550 And then it turned out to be Morris price in. Some of you might remember who knew a downside more about this than I ever will. 215 00:28:46,550 --> 00:28:57,990 But the key thing is the electron interacts with magnetic fields, the same interaction the nuclei interact with. 216 00:28:57,990 --> 00:29:07,220 That was just it. The magnetic fields that we have, there's a topping out of that nucleus in the fraction. 217 00:29:07,220 --> 00:29:12,050 The Electrum also interacts with electric fields, 218 00:29:12,050 --> 00:29:22,850 and we can get spins that are not a half because we can couple two electrons together to produce something that has an effective spin of one. 219 00:29:22,850 --> 00:29:26,330 I use the term effective very carefully because you've got two spin off one. 220 00:29:26,330 --> 00:29:37,070 Some were able to spin off that we usually ignore, but it is there so we can have interactions with the nuclei with the quad core moment. 221 00:29:37,070 --> 00:29:41,960 We can have interactions between distant electrons like two electron interactions. 222 00:29:41,960 --> 00:29:47,340 I'm already seeing the high profile interaction, the interaction between the electron spin and the nuclear spin. 223 00:29:47,340 --> 00:29:57,680 So all of these terms come into play, and it's a matter of spotting which are important, which are not. 224 00:29:57,680 --> 00:30:00,620 So I've just got three slides, I'm with these, 225 00:30:00,620 --> 00:30:12,860 I'm just trying to emphasise again the impact that the work of Blini Baker and many others in the Clarendon have. 226 00:30:12,860 --> 00:30:18,740 So, Arjun, you recognise and perhaps, Chris, 10ml as well from chemistry here in Oxford, 227 00:30:18,740 --> 00:30:24,860 so in Oxford, there is the centre for advanced electron spin resonance, which is well resourced. 228 00:30:24,860 --> 00:30:30,170 They don't have enough money heads department. They need more money because it's really important research. 229 00:30:30,170 --> 00:30:36,730 If ever Arjun asks for anything, give it to him straight away without thinking. 230 00:30:36,730 --> 00:30:44,380 But it has many uses, you'll see one hundred and forty trained uses here, teach teaches undergraduates as well. 231 00:30:44,380 --> 00:30:58,690 Very good publication record of really excellent science. Apia now is a resource that can be used by many uses across entire science faculties. 232 00:30:58,690 --> 00:31:06,760 This is a similar slide from the University of Manchester, where they host the national EPR facility. 233 00:31:06,760 --> 00:31:16,430 It's not as good as the Oxford Prof. Yeah, but again, as in a whole range of science is enabled. 234 00:31:16,430 --> 00:31:28,850 And there has been a great tradition that really started in the clarendon of the development of state of the art hardware for magnetic resonance. 235 00:31:28,850 --> 00:31:43,370 And this is an example from University of St. Andrews, some of Graham Smith's work where they are developing high field, high frequency EPR. 236 00:31:43,370 --> 00:31:49,370 And Graham describes it as bringing the NMR paradigm to EPA. 237 00:31:49,370 --> 00:31:53,420 The fields really developed together, 238 00:31:53,420 --> 00:32:03,890 but then in the 1970s diverged with the invention of the fast ferry transform and the RF hardware that made it possible 239 00:32:03,890 --> 00:32:13,460 to do time domain NMR to produce RF pulses on a timescale that was short compared to nuclear relaxation time. 240 00:32:13,460 --> 00:32:18,920 So the whole field of NMR virgins and you've got a magnetic resonance imaging, 241 00:32:18,920 --> 00:32:27,590 as well as all the spectroscopy that simply wasn't possible for EPR because the interactions of the 242 00:32:27,590 --> 00:32:35,730 electrons were so much stronger and the relaxation times were so much shorter that you needed. 243 00:32:35,730 --> 00:32:43,440 Pulses. Of sub nanosecond in sub nanosecond that simply couldn't be achieved. 244 00:32:43,440 --> 00:32:50,700 So EPR ends of the doldrums a little bit because the technology wasn't there to develop it. 245 00:32:50,700 --> 00:32:58,260 But now with a lot of microwave comms technology, that has changed so. 246 00:32:58,260 --> 00:33:02,550 Pulsed EPR is now widespread. Yeah. 247 00:33:02,550 --> 00:33:06,090 And Brooker actually told me confidentially, 248 00:33:06,090 --> 00:33:13,590 I was always told an Oxford secret is something you tell one person at a time that they are the solid state animal. 249 00:33:13,590 --> 00:33:27,510 They sell more EPR machines than they do solid state NMR machines. So I want to give you a few examples of how EPR is used today. 250 00:33:27,510 --> 00:33:36,730 So. I've already mentioned that gamma ray radiation is used for sterilisation. 251 00:33:36,730 --> 00:33:43,510 It's used to sterilisation of things that you can't heat up because they are unstable, 252 00:33:43,510 --> 00:33:56,730 but you still want to kill bacteria and suchlike and that is used for some foodstuffs, and it is also used widely in the pharmaceutical industry. 253 00:33:56,730 --> 00:34:02,170 And lots of the things that firmly degrade very easily are irradiated. 254 00:34:02,170 --> 00:34:14,450 Yeah. And that can include the excipients and the API says, because the active pharmaceutical ingredient. 255 00:34:14,450 --> 00:34:22,710 And you have to sort of worry about irradiation because it is going to produce electrons, 256 00:34:22,710 --> 00:34:30,230 is going to break free electrons, is going to break bonds, you're going to end up with radicals. 257 00:34:30,230 --> 00:34:36,290 So a commonly used exhibit, excipients in paracetamol, in the tablets. 258 00:34:36,290 --> 00:34:46,180 Yeah, it's a histamine. And if you gamma ray, irradiate the history, you make a whole fistful of radicals at room temperature, 259 00:34:46,180 --> 00:34:53,560 there are lots of interactions and you end up with this radical, which is a D ammunition radical. 260 00:34:53,560 --> 00:35:04,090 This A92 group has fallen off. And this radical in the powder is very stable and very, very long left. 261 00:35:04,090 --> 00:35:07,720 Yes. And. 262 00:35:07,720 --> 00:35:19,930 People thought, well, that doesn't really matter, because the moment I put this radical into solution into water as it's a carbon centred radical, 263 00:35:19,930 --> 00:35:27,670 it's going to be very reactive and before it gets near a patient, it's going to have gone. 264 00:35:27,670 --> 00:35:35,680 A good assumption. Yeah. But these things that have a very short life and solution are very difficult to detect. 265 00:35:35,680 --> 00:35:42,260 So there's a whole field of spin tracking. It's called by the chemists. 266 00:35:42,260 --> 00:35:47,840 And these are clever molecules that such as this MMP, I can't pronounce it. 267 00:35:47,840 --> 00:36:01,010 That's why getting the acronym MMP, this reacts with the radical sets that the radical is now ex is bonded to this spin. 268 00:36:01,010 --> 00:36:06,730 Trap and spin trap of who long lived. So. 269 00:36:06,730 --> 00:36:15,110 This was dissolved, the radioactive had it was dissolved in a solution containing the spin from. 270 00:36:15,110 --> 00:36:25,420 And now you're all experts on analysing hot find for actions. So you see, we've put the unpaired electron, which is on this new bond. 271 00:36:25,420 --> 00:36:34,220 Where it sounded, so there's a proton nearby and then there's two protons a little bit further away that are roughly equivalent. 272 00:36:34,220 --> 00:36:42,320 So one Proton is going to split the spectrum into two. 273 00:36:42,320 --> 00:36:48,560 And turbulent times, we've seen this will split the spectrum into one to one. 274 00:36:48,560 --> 00:36:56,210 But the nitrogen is also there, the nation has a nuclear spin of one, so that's going to split the spectrum into three one two three. 275 00:36:56,210 --> 00:37:00,650 This proton splits off into to these two protons for one two one. 276 00:37:00,650 --> 00:37:08,330 And that's experimental spectrum. There's a simulated spectrum. There is no doubt that this is the radical that has been spin fact. 277 00:37:08,330 --> 00:37:13,590 And now we can study. No. So fun. 278 00:37:13,590 --> 00:37:19,230 Yeah. But what we hadn't thought about. 279 00:37:19,230 --> 00:37:28,890 Was that when the irradiation was done? There are other things present in the powder like water, like oxygen. 280 00:37:28,890 --> 00:37:34,170 And actually, you can generate some very aggressive oxidants. 281 00:37:34,170 --> 00:37:41,760 Yeah. And they will probably react with radicals like this or might even hang around in other forms. 282 00:37:41,760 --> 00:37:51,350 And you think as well as probably all right. But of course, this solution is injected into the patient with a needle. 283 00:37:51,350 --> 00:37:54,870 And that needle has a little bit of iron in it. 284 00:37:54,870 --> 00:38:03,960 And that iron can drive what is called phantom chemistry that can interact with things like hydrogen peroxide and produce hydroxyl radicals, 285 00:38:03,960 --> 00:38:11,870 which in turn will attack the highest of things and produce the de emanation radical. 286 00:38:11,870 --> 00:38:20,130 So lo and behold. If you use a metal needle, dissolve insulation and inject it, 287 00:38:20,130 --> 00:38:27,990 the little bit of trace on generating this radical for hours after you've mixed installation is not short lived, 288 00:38:27,990 --> 00:38:32,140 it is short lived, but you keep regenerating more and more of it. 289 00:38:32,140 --> 00:38:42,680 So we did this work with a pharmaceutical company. They actually stopped production of everything that involved irradiation to check. 290 00:38:42,680 --> 00:38:52,570 That they weren't radiating. Anything with histidine in it because they were very smart company with this very quickly. 291 00:38:52,570 --> 00:38:59,740 But they were really worried that you could get radical induced degradation of the drug and free radicals injected. 292 00:38:59,740 --> 00:39:12,090 The patient could potentially kill the patient. So it's an example where EPA was really the tool of choice to study the system. 293 00:39:12,090 --> 00:39:17,010 Here is another example this work is led by Peter Sadler in Warwick. 294 00:39:17,010 --> 00:39:26,260 These platinum complexes with these photoreceptors attached to them are potentially very useful anti-cancer drugs. 295 00:39:26,260 --> 00:39:34,680 And when you shine light on them, you can actually generate you can change the charge, 296 00:39:34,680 --> 00:39:43,420 save the platinum and kick off a radical hydroxyl radicals and other radicals. 297 00:39:43,420 --> 00:39:48,610 Here is three nights this radicals kicked off and spin trapped, 298 00:39:48,610 --> 00:39:55,450 so it actually has a dual attack on the cancer cells, both the radicals and the platinum to attacks the cells. 299 00:39:55,450 --> 00:40:00,480 But the beauty is that you can inject this harmless. 300 00:40:00,480 --> 00:40:07,050 If you can make it be pretty concentrated in the cancer cells, then just illuminate them. 301 00:40:07,050 --> 00:40:15,450 And for skin cancers, that is possible, then you can locally kill the cell and the mechanism is not fully understood yet, 302 00:40:15,450 --> 00:40:28,120 but we have shown this is definitely the radical and the platinum. And again, this is where this sort of work couldn't be done without EPO. 303 00:40:28,120 --> 00:40:38,040 So. As Robert said, I couldn't resist not talking about Diamond a little bit. 304 00:40:38,040 --> 00:40:46,770 Now. I've said the electron is very sensitive to its environment. 305 00:40:46,770 --> 00:40:55,190 Really, for many quantum applications, we want our quantum system to be really isolated from the environment. 306 00:40:55,190 --> 00:41:00,720 Lastly, diamonds not a bad, solid state vacuum because it's made out of carbon. 307 00:41:00,720 --> 00:41:10,850 You make out of carbon 12, there's no nuclear spins. And if all of the bonds are perfectly formed and diamonds, there are no unpaired electrons. 308 00:41:10,850 --> 00:41:14,720 All the electrons are paired up, making the strong bonds. 309 00:41:14,720 --> 00:41:26,220 So if we put the occasional defect in diamonds, we potentially have a resource for quantum technologies. 310 00:41:26,220 --> 00:41:35,280 And this is a defect in Diamond, so you can see most of the carbon atoms, here are four fold coordinates of expect the diamond. 311 00:41:35,280 --> 00:41:42,260 But there's one missing. And there's one being replaced by a nitrogen imperative. 312 00:41:42,260 --> 00:41:48,730 So we have a nitrogen next to a vacancy, the so-called nitrogen vacancy centre. 313 00:41:48,730 --> 00:41:54,710 And we're coming in a couple of years time to impact studies and rest. 314 00:41:54,710 --> 00:41:59,240 This defect was discovered in the very early 1970s. 315 00:41:59,240 --> 00:42:04,940 You'll see in a minute single centre detection is possible, but applications have only just started happening, 316 00:42:04,940 --> 00:42:09,890 and this is the number of papers published per year on this defect. 317 00:42:09,890 --> 00:42:15,160 Sometimes things take a long time before people realise that important. 318 00:42:15,160 --> 00:42:23,940 So we're just going to do something that was developed in Oxford. 319 00:42:23,940 --> 00:42:35,640 And which is a really useful approach. And this goes back to Charles Colson and a Ph.D. student, it really deserves an awful lot of credit for this. 320 00:42:35,640 --> 00:42:39,480 Mary Kissling And we're now back in 1957, 321 00:42:39,480 --> 00:42:50,760 so only about 10 years after FDR was developed and people are getting interested in defects in solids that were paramagnetic. 322 00:42:50,760 --> 00:43:01,620 So they could sit in case they came up with the concept of a defect molecule approach, which is a really nice way of analysing this map. 323 00:43:01,620 --> 00:43:07,840 So this defect is in diamond. Yeah. Ignore the diamond. 324 00:43:07,840 --> 00:43:15,550 Now, all the electrons are paid off in strong bonds, we can ignore that large band gap material operating the band gap. 325 00:43:15,550 --> 00:43:24,160 But what we have to worry about are the dangling orbitals where we've extracted this carbon atom to make the vacancy and the impurity. 326 00:43:24,160 --> 00:43:33,670 So effectively, we've got one two three four dangling over this, and we clearly have an axis of symmetry of the defect along the nitrogen vacancy. 327 00:43:33,670 --> 00:43:43,720 So these three are all related by a three fold rotation so we can derive all of the electronic 328 00:43:43,720 --> 00:43:49,390 properties of this by treating it as a molecule just considering the dangling orbitals. 329 00:43:49,390 --> 00:43:57,580 Well, the nitrogen is different, the rest. So here we will generate a wave function just using the nitrogen. 330 00:43:57,580 --> 00:44:01,600 These carbons, they're upset they would like to be bonded to other carbons. 331 00:44:01,600 --> 00:44:06,500 They'll try and bond with each other, so we'll produce a bonding over the. 332 00:44:06,500 --> 00:44:09,330 With the three cardinal. 333 00:44:09,330 --> 00:44:16,110 And then they produced a bonding of little we're going to produce some anti bonding orbitals and there's a couple of ways of doing it. 334 00:44:16,110 --> 00:44:21,870 And a chemist who does group therapy will just be crying now as they might just obliterated that. 335 00:44:21,870 --> 00:44:26,670 But. We generate two singlets and a double. 336 00:44:26,670 --> 00:44:36,510 If this defect is in the negative charge state, we have one two three four five six electrons, the extra electron being donated by some donor. 337 00:44:36,510 --> 00:44:46,290 So we have to populate these energy levels one to pad up, one to pad up and now one two, we can have them spend per cent, pilots say. 338 00:44:46,290 --> 00:44:53,130 So we can generate an X equals one state. We can also generate some spin zero states as well. 339 00:44:53,130 --> 00:45:02,530 If we were to shine some light and excite an electron from this, a state that each state which is not full, we can generate some excited states. 340 00:45:02,530 --> 00:45:07,530 Yeah, and actually this could be an optical transition. 341 00:45:07,530 --> 00:45:17,740 This approach works brilliantly, and in the true way of doing physics has been reinvented every 10 years since 1957 as the way to do it. 342 00:45:17,740 --> 00:45:22,290 We can generate the ground state. 343 00:45:22,290 --> 00:45:29,020 The 380 and but remember, this is not a vacuum, the atoms are vibrating. 344 00:45:29,020 --> 00:45:35,470 So actually, the electronic states are coupled the vibrations that we have, these vibrant states. 345 00:45:35,470 --> 00:45:39,670 Here is the three state and we have a couple of segments as well. 346 00:45:39,670 --> 00:45:47,080 So actually, we can shine some green light or even shorter wavelength and get optical absorption. 347 00:45:47,080 --> 00:45:54,360 We're not doing EPR anymore. We're doing electric dipole transitions. We're frying electrons between the energy levels. 348 00:45:54,360 --> 00:46:04,360 It will rattle down losing vibration energy and then sit here for a while and then fall back to the ground state, emitting some red light. 349 00:46:04,360 --> 00:46:12,630 So we have optical absorption with the short wavelength, an optical emission with the longer wavelengths. 350 00:46:12,630 --> 00:46:23,090 And this little box here is produced by De Beers for distinguishing between. 351 00:46:23,090 --> 00:46:28,830 A natural and synthetic diamonds. 352 00:46:28,830 --> 00:46:34,290 And. Is basically a little UV source. 353 00:46:34,290 --> 00:46:45,900 We are now in the period where we do have to worry about health and safety, so I can't shine the UV source around the lab. 354 00:46:45,900 --> 00:46:53,620 If I remember. Come on, wake up. 355 00:46:53,620 --> 00:47:01,640 Yes, that. So I have here a little diamonds. 356 00:47:01,640 --> 00:47:08,890 If I can switch the. Components a bit small as the pump, so we can. 357 00:47:08,890 --> 00:47:21,460 Suck, the pump comes alive if I drop the diamond, don't all rush at once to pick it up. 358 00:47:21,460 --> 00:47:34,340 So now hopefully, we can see the nicely polished diamond. And rather than using green light, we're going to switch the Navy lamp on. 359 00:47:34,340 --> 00:47:40,780 And we can see the diamond is glowing, a nice orange colour. 360 00:47:40,780 --> 00:47:49,560 This is a synthetic diamonds grown in the lab, specifically with the nitrogen vacancy defects in. 361 00:47:49,560 --> 00:47:58,420 So that we are sitting up and we are missing this red orange light. 362 00:47:58,420 --> 00:48:09,850 We can do that in a more complicated way, and this can total photoluminescence microscope was part funded by the Office of Quantum Technology Hub. 363 00:48:09,850 --> 00:48:23,540 But effectively is doing some of the same things. We have laser light that is directed onto the sample and we're collecting the light that is emitted. 364 00:48:23,540 --> 00:48:36,420 Now, this is the image of another Diamond. A very high purity diamond grown by Element six on the Harwell campus. 365 00:48:36,420 --> 00:48:43,020 And these little dots, this is an image taken in the confocal microscopy, you can see the scale bar has five microns. 366 00:48:43,020 --> 00:48:50,500 Each of these little dots is an individual nitrogen vacancy centre luminescent. 367 00:48:50,500 --> 00:48:55,030 Just one. I can see you don't believe him. 368 00:48:55,030 --> 00:49:06,980 Yeah. So we can actually look at the life that's being admitted in an optical transition by one of these defects and send it through a beam splitter. 369 00:49:06,980 --> 00:49:12,620 So if this is a single defect emitting one photon at a time, the photon has a choice. 370 00:49:12,620 --> 00:49:18,900 They can go up to detector two or straight through the detector one. 371 00:49:18,900 --> 00:49:26,520 So we can look at the statistics of the arrival of photons at these two detectors. 372 00:49:26,520 --> 00:49:32,430 And if this is a single photon source, I won't defect. 373 00:49:32,430 --> 00:49:34,630 It emits a photon. 374 00:49:34,630 --> 00:49:42,820 It has to be then reignited back to the excited state, and the average lifetime is about 10 nanoseconds before it can make another one. 375 00:49:42,820 --> 00:49:47,710 It can't be to photons at the same time. 376 00:49:47,710 --> 00:49:56,770 So if we plot the probability of arrival of photons, the correlation between the rivals that detect one and detector two, 377 00:49:56,770 --> 00:50:05,670 we see if the time difference between the detectors is zero, we get a zero correlation. 378 00:50:05,670 --> 00:50:10,290 We don't have photons arriving both detectors at the same time. 379 00:50:10,290 --> 00:50:13,200 If we have a big time difference between them, we do. 380 00:50:13,200 --> 00:50:23,130 If we actually have more than two levels as we do for the Nation Vacancy Centre, we can have a vote on bunching as well as the anti. 381 00:50:23,130 --> 00:50:35,250 But this measurement is done at Warwick in an undergraduate lab on a single envy centre, at room temperature in approximately 30 seconds. 382 00:50:35,250 --> 00:50:45,580 To get statistics so you prove that it is a single emitter, a single defect that is emitting the light. 383 00:50:45,580 --> 00:50:54,970 But we've forgotten about the fact that the ground state had an electron spin of one, the ground state is paramagnetic. 384 00:50:54,970 --> 00:51:03,760 So in a magnetic field, we can split the plus one minus one level and we can drive EPR transitions between them. 385 00:51:03,760 --> 00:51:17,550 We can do magnetic resonance. Now, if you're selling this is a design feature, if you're truthful, it's an accident. 386 00:51:17,550 --> 00:51:25,410 If you happen to be in the spin, not state and excite up with your green light with 99 percent probability, 387 00:51:25,410 --> 00:51:31,540 you emit a red photon and come back to the state. Right, exactly what you want. 388 00:51:31,540 --> 00:51:38,990 If you're in the plus or minus one state and you absorb the green photon. We very rarely do you come back. 389 00:51:38,990 --> 00:51:49,370 Most of the time you cross over to some of the singlet states, emits an infra-red photon and arrive back at the north state. 390 00:51:49,370 --> 00:51:58,170 This is brilliant. Because with three photons absorb it doesn't matter which state you are in. 391 00:51:58,170 --> 00:52:06,600 You will find yourself with a ninety nine point nine nine percent fidelity in the middle equals not state. 392 00:52:06,600 --> 00:52:17,130 Just by shining the laser pointer, the green laser pointer onto the diamond, you prepare your quantum system in the spin, not state. 393 00:52:17,130 --> 00:52:22,590 Spin initialisation. We're not talking about 10 to the 12. 394 00:52:22,590 --> 00:52:28,700 We're talking about one. It's been we prepared in a state. 395 00:52:28,700 --> 00:52:33,290 If we do some magnetic resonance, we need a magnet. Yeah. 396 00:52:33,290 --> 00:52:40,830 So rather than having a big magnet that we have a little near the magnets on a little robot so we can move the magnets around. 397 00:52:40,830 --> 00:52:50,600 We can drive an EPR transition between the two levels. Now, remember, in this level, excite image, this is bright. 398 00:52:50,600 --> 00:53:00,170 It just goes round this cycle and emits very efficiently. If we drive an EPR transition and put it out of the state into plus minus one state, 399 00:53:00,170 --> 00:53:11,730 doesn't it make the red photons so efficiently and the fluorescence intensity when we hit the EPR transition drops? 400 00:53:11,730 --> 00:53:20,440 This is fluorescence data on a single nation vacancy centre recorded by undergraduates. 401 00:53:20,440 --> 00:53:28,180 A 30 percent change in the first is nothing fancy here, just the microwave switched on continuously and the laser run continuously. 402 00:53:28,180 --> 00:53:32,200 You can do clever experiments with laser pulses, microwave pulses. 403 00:53:32,200 --> 00:53:41,300 But here we have spin manipulation of a single electron trap this nation baking centre. 404 00:53:41,300 --> 00:53:46,130 So we have optical image stabilisation showing the green light on. 405 00:53:46,130 --> 00:53:57,360 We have spin manipulation by microwave light and we can read out which state it is in by looking at the very essence of the defect. 406 00:53:57,360 --> 00:54:05,890 We have everything we need for optically detected magnetic resonance on a single spin. 407 00:54:05,890 --> 00:54:10,760 So now this is EPR future. 408 00:54:10,760 --> 00:54:20,220 Here we have it, and I sent it with a little diamond at the end of it with an envy centre in here is a microwave excitation. 409 00:54:20,220 --> 00:54:28,020 Here's our microscope objective. This single atomic defect the size of an atom. 410 00:54:28,020 --> 00:54:34,970 We can read out at room temperature and it can measure magnetic fields. 411 00:54:34,970 --> 00:54:40,760 This is a product made by A., which is exactly this device. 412 00:54:40,760 --> 00:54:55,280 And actually. The spin sensitivity is such that this envy defect can detect the magnetic field associated with a single proton. 413 00:54:55,280 --> 00:55:07,820 Anybody who does anymore throw away your magnets now. No field NMR with atom by atom detection is coming. 414 00:55:07,820 --> 00:55:14,690 These are some colleagues in Oxford. They fail to recognise Mark Smith is now vice chancellor, Lancaster and Stephen Brown, 415 00:55:14,690 --> 00:55:21,470 who runs our solid state animal facility standing in front of a three and a half million pound magnet for animal, 416 00:55:21,470 --> 00:55:27,760 gets up to 850 megahertz for protons. They've just funding for a gigahertz machine. 417 00:55:27,760 --> 00:55:42,310 NMR is brilliant, but the sensitivity is lousy, so you need to go to very high magnetic fields to generate enough magnetisation to be able to detect. 418 00:55:42,310 --> 00:55:51,160 There are solutions now, and I put this in because they are working with my kids in the audience here. 419 00:55:51,160 --> 00:55:57,070 Rabbits Lady got really interested in dynamic nuclear polarisation that's transferring 420 00:55:57,070 --> 00:56:03,670 polarisation from electrons to nuclei to increase the sensitivity of NMR. 421 00:56:03,670 --> 00:56:11,770 And if you have a nanodiamonds with your primary defect, then especially like the notion that you can spin polarised, 422 00:56:11,770 --> 00:56:17,530 you can transfer that polarisation to the carbon 13 nuclei around it. 423 00:56:17,530 --> 00:56:23,110 And that's 25 times the animal signal from the carbon 13. 424 00:56:23,110 --> 00:56:29,980 This is now with the dynamic of the polarisation shine a laser onto sample polarised electrons, 425 00:56:29,980 --> 00:56:35,410 transfer the polarisation from electrons to nuclear massive increase in sensitivity. 426 00:56:35,410 --> 00:56:44,140 OK, getting the polarisation out of the nano diamond into the molecules of interest is more difficult, 427 00:56:44,140 --> 00:56:54,820 but we don't have factors of 200 yet, but we do have factors of 20, which is a saving in experimental time of 400. 428 00:56:54,820 --> 00:57:01,920 And this is potentially an MRI contrast agents with excellent sensitivity, so. 429 00:57:01,920 --> 00:57:10,590 EPR is really, I think, in the next 10 years going to help animal out a lot because that is a potential 430 00:57:10,590 --> 00:57:16,560 not only to detect individual nuclear spins individual electrons is easy. 431 00:57:16,560 --> 00:57:27,640 Now with this approach, but also in our classical NMR approach to really boost the sensitivity by many orders of magnitude. 432 00:57:27,640 --> 00:57:35,440 I'm nearly done. I just want to show you another example. This is colleagues at Harvard University. 433 00:57:35,440 --> 00:57:41,320 This is a cell. OK, so pitch fossil. I don't know what the cell looks like, but it's a picture of cell and inside the cell. 434 00:57:41,320 --> 00:57:46,570 We have a couple of nanodiamonds, so there's work going on in the in the audience here in Oxford, 435 00:57:46,570 --> 00:57:53,020 making it functional, using fluorescent nanodiamonds that we can use in biological applications. 436 00:57:53,020 --> 00:57:58,330 And of course, I should have pointed out that the surface of the Nano Diamond isn't perfect diamond. 437 00:57:58,330 --> 00:58:04,460 It's all sorts of things going on the surface that we have to try and control the surface. 438 00:58:04,460 --> 00:58:09,230 But the idea was that these nanodiamonds are in the South. 439 00:58:09,230 --> 00:58:15,470 Yeah. And actually, this zero field splitting is temperature dependent. 440 00:58:15,470 --> 00:58:19,880 So if we're at zero field, at room temperature, we get one line. 441 00:58:19,880 --> 00:58:25,150 If we put the magnetic field on and split the plus and minus one transitions, we get two lines. 442 00:58:25,150 --> 00:58:37,870 If the temperature changes, those two lines shift. So it's been shown already that EPR detected by the Night and Vacancy Centre 443 00:58:37,870 --> 00:58:45,040 can measure the temperature way in optimal cases Milli Kelvin sensitivity. 444 00:58:45,040 --> 00:58:47,440 Melanie Kelvin sensitivity. 445 00:58:47,440 --> 00:58:57,290 And already it's been shown that it is possible to show that cancerous cells that have a higher metabolic rate are running slightly hotter. 446 00:58:57,290 --> 00:59:02,530 The normal cells. You can measure the temperature inside the cell, 447 00:59:02,530 --> 00:59:08,980 and it's now being shown that that's actually got very little to do with the temperature of the solution around these temperature variations. 448 00:59:08,980 --> 00:59:16,250 But the idea was. To put gold nanoparticles and at the same time. 449 00:59:16,250 --> 00:59:23,810 And actually make a hybrid gold nanodiamonds that maybe coat the diamond partially. 450 00:59:23,810 --> 00:59:31,330 Because then you could identify which cells were cancerous and then cook them. 451 00:59:31,330 --> 00:59:37,970 To kill them. A bizarre idea for the patents being granted. 452 00:59:37,970 --> 00:59:44,030 Yeah. And I couldn't resist this slide. 453 00:59:44,030 --> 00:59:55,530 Yeah. So this was an experiment that was done in 2015 by Ronald Hanson's group at the University of Delft. 454 00:59:55,530 --> 01:00:00,090 So we're doing quantum entanglement, hit a pair of particles interact, 455 01:00:00,090 --> 01:00:04,680 such as the quantum state of each particle cannot be described independently at the stage of the other, 456 01:00:04,680 --> 01:00:14,100 even when the particles are separated by a large distance. So here we have two diamonds with that EPR defect that night and back the centre. 457 01:00:14,100 --> 01:00:22,610 One of them, they. Manipulate it with microwaves and read out optically initialised and read out optically. 458 01:00:22,610 --> 01:00:31,100 And these two diamonds, so rather than being three metres apart, they were moved to 1.3 kilometres apart. 459 01:00:31,100 --> 01:00:43,880 They were entangled. The two spins that were in this state, such that the properties, the two particles were correlated. 460 01:00:43,880 --> 01:00:49,270 So if you make an observation on one, you know, the state of the other. 461 01:00:49,270 --> 01:00:58,020 So Einstein didn't like this. This is a spooky action with this and the paper published by Einstein, Podolsky and Rosen. 462 01:00:58,020 --> 01:01:05,090 Known as the EPR paradox, the other EPR. 463 01:01:05,090 --> 01:01:11,300 This experiment had the diamonds far enough apart that a loophole was closed, 464 01:01:11,300 --> 01:01:18,170 that it was not possible for information to travel at the speed of light from one diamond the other. 465 01:01:18,170 --> 01:01:27,520 So they proved as one of the experiments that has shown this idea of simple possession. 466 01:01:27,520 --> 01:01:35,040 So the point I wanted to make with this experiment is that NPR has come back full circle. 467 01:01:35,040 --> 01:01:44,060 It is now an active area and an EPR Jason's materials department, as well as welcome to physics. 468 01:01:44,060 --> 01:01:54,920 But it is a technology, not a technology that can be used for sensing very weak magnetic fields. 469 01:01:54,920 --> 01:02:03,680 A paper came out in a US journal last week on detecting large metal objects under the water. 470 01:02:03,680 --> 01:02:10,520 Using night and balancing magnetometers. 471 01:02:10,520 --> 01:02:20,420 But you can do it on very small length scales, detecting magnetic nanoparticles and even, I think in the future individual atoms. 472 01:02:20,420 --> 01:02:28,190 But also you've got a resource for quantum technology, you've got a spin that you can control and manipulate. 473 01:02:28,190 --> 01:02:42,560 And there's a lot of great work in Oxford and actually writing defects into the diamonds to be able to to correct the defects on demand. 474 01:02:42,560 --> 01:02:50,480 I'm going to stop now, but I'll put up a picture of the diamond at the end, this synthetic diamond grown by Element six. 475 01:02:50,480 --> 01:02:57,380 I've got another one that I'll put up there was actually I bought for my wife. 476 01:02:57,380 --> 01:03:00,980 Now she's let me have it today. As in the coming, have a look at the end. 477 01:03:00,980 --> 01:03:07,250 It's a nice little pink stone with nice and vacancy and $800 a carat. 478 01:03:07,250 --> 01:03:10,880 Buy them online. I'm not on commission, 479 01:03:10,880 --> 01:03:24,770 but this diamond has actually been engraved using a technique developed here in Oxford with a little logo about 200 microns beneath the surface, 480 01:03:24,770 --> 01:03:35,120 produced there by femtosecond laser writing. And the same technology can be used to write with a precision of tens of nanometres, 481 01:03:35,120 --> 01:03:40,430 maybe 30 nanometres individual nitrogen vacancy defects into diamond. 482 01:03:40,430 --> 01:03:46,810 So this is some excellent work that is going on in Oxford. 483 01:03:46,810 --> 01:03:59,020 Building upon. EPA. So I'd just like to thank all of the students and post-docs involved in this work. 484 01:03:59,020 --> 01:04:04,240 But we are doing and others are doing in the UK and overseas. 485 01:04:04,240 --> 01:04:12,040 And of course, the funding bodies. But really, I am trying to make the point. 486 01:04:12,040 --> 01:04:17,500 That's. Back in the nineteen forties. 487 01:04:17,500 --> 01:04:23,790 So we are talking about 70 years ago now. 488 01:04:23,790 --> 01:04:36,720 The technology was developed to be able to understand what these spins were doing, what they were interacting with and what environments they were in. 489 01:04:36,720 --> 01:04:46,450 That has developed into a whole field of spectroscopy and is now evolving again into a whole new technology. 490 01:04:46,450 --> 01:04:51,220 But that technology is just electron paramagnetic resonance. 491 01:04:51,220 --> 01:04:58,005 So its home is here. Thank you very much.