Identify chemicals with radio frequencies - Nuclear Quadrupole Resonance (MRI without magnets)

today on applied science we're going to be doing some Nuclear Physics I want to show you this little known technique of doing chemical identification that works even through a sealed container so we're going to put the sample in a coil of wire and transmit and receive and determine what chemical is in the coil a pretty cool technique and in this video I'm going to show you the Practical side of building the spectrometer itself the RF tuning and isolation techniques tuning it with a nano VNA and then I'll talk about the Nuclear Physics what's actually going on with the particles and just the first step of quantum mechanics okay so let's see a demonstration of this whole thing I'm going to start the transmit process by pressing the burst button on the oscilloscope and what this is going to do is create a transmit pulse using the Scopes function generator which then gets Amplified and sent down to the box here Amplified and then put into that coil of wire then there's the scope is going to delay about 200 and so microseconds and then start to receive and collect everything from that coil and what we're looking at here is a spectrum a frequency domain of what we got back from the coil so pretty big spike there and this is coming from sodium nitrite which is the chemical that I've Got Loaded into that coil and sodium nitrite has a characteristic frequency at about 3.6 megahertz and this frequency is universal so if we were talking to you know intelligent life forms on the other side of the Galaxy they would also agree that sodium nitrite has a resonant frequency at 3.6 megahertz and the cool thing is we wouldn't have to know anything about the periodic table or physics or constants or anything as long as we agreed upon a time like what a you know a Hertz is or what a second is all these nqr frequencies for all the compounds in the world are the same across everywhere a universal So currently the signal we're getting from sodium nitrate is actually quite high and every time I press the burst button it's a single experiment so we're not averaging anything here but what we can also do is turn on averaging so we'll do like 10 shots and each time the experiment runs we're just averaging the frequency Trace over and over again and so as we do more and more averages you can see that the noise goes away and hopefully the signal stays High and there you go okay so now you might be thinking well if we're transmitting at such a high power at the same frequency that we're looking for maybe it's just the coil still ringing down so what we'll do is take out the sample of sodium nitrate and put in a sample another nitrogen compound urea and we'll run the burst and as you can see there's no hint of a signal there from urea and we'll put in some table salt which doesn't have nitrogen in it at all and you'll see why I keep saying nitrogen because that's going to become an important thing and if we go back to the sodium nitrite sample the signal is So High by the way that we don't even need the Box closed we're actually getting enough signal even in one burst it's pretty obvious that it's there even in a single shot if we're looking for a much smaller signal it seems to be going down a bit there but if we're looking for a much weaker signal it might be down in the noise and so then what you have to do is close the Box because this is a really sensitive instrument and then average a ton of uh of readings to get anything to look at it through the noise so as it happens sodium nitrite is just very strong and it's a great way to test if your system is working but if you're looking for something you know more mundane something more difficult or something that you might encounter in the real world you might need more advanced you know techniques to get the signal out keep in mind that we're transmitting it maybe 10 or 50 watts and we're receiving it Pico watts and so the the amount of signal loss is pretty massive and that's why it requires all this weird RF stuff in the copper box and everything let's talk about that weird RF stuff here's a system plan and you'll see that the entire thing is driven by the oscilloscope so the function generator within the oscilloscope produces the transmit pulse which is about 100 microseconds at 3.6 megahertz and we feed that right into a power amplifier this is the blue piece of equipment sitting on the bench there and by the way this was kindly donated by a viewer named Ian so thank you very much Ian and we're actually operating your amplifier a little bit outside its frequency range so even though it's rated for plus 56 DB the fact that we're outside the range a little bit means we may not be getting quite that much gain but nonetheless we're probably at around 25 watts for the transmit pulse and everything in the circuit from here to here is 50 ohms so we send this 50 ohm 25 watt pulse out into here and we use this matching capacitor this is one of those variable variable vacuum capacitors that you saw in the box and we feed that into this parallel LC resonance circuit and the L in the parallel circuit is the sample coil so this is that coil of wire that's holding the test tube and it's about 25 turns and we use this relatively thick wire because we want a very high Q when you read articles about nqr and this this technique that we're doing here everyone talks about getting the cue of your of your sample higher and higher as it turns out there are other facets of this thing that might be even more important than the queue of the probe here but the reason that it's a thing that you might want to worry about is that the higher the queue of this resonance circuit the easier it is to detect a very weak signal so what we want to do is detect just the tiniest amount of of magnetic variation within that coil and if our Q is really high that means it can sort of build up a high signal because you've got this really resonant circuit ready to kind of store up energy from this very weak signal that we're going to get from Atomic nuclei right so it's not going to be very strong so that's kind of the transmit side and then we take the signal and feed it into a 60 DB low noise amplifier and then put it right back into the oscilloscope so you can see we could we're going to have some problems here if we built it as is we've got 25 watts coming out and then it's sent right into this sensitive low noise amplifier so it would immediately destroy the amplifier if we set it up this way so the first thing we need to do is figure out how we're going to separate the transmit and the receive channels and we could use a transmit receive switch like a physical relay or something that would work but the problem is that our timing is pretty critical so we've got this 100 microsecond pulse and then we want to wait maybe one or two hundred microseconds and then start receiving right away and timing a physical switch to within you know tens or hundreds of microseconds it's not going to be that easy so we could also use a solid state switch like an active switch pin diode or a mosfet or something like that and those are good choices but as it turns out there's a completely passive way to do it what we're going to do is build a circuit that behaves differently whether it's passing high power or low power and here's what it looks like this technique is well known it's called like a Lambda over four technique a quarter wavelength technique and I first learned about this on W2 aew's YouTube channel Alan has a ton of RF videos and I've probably learned more about RF from his videos than anywhere else and there's also some good sources that I'll put in the description that discuss how this relates specifically to magnetic resonance or nuclear resonance experiments but the idea is that we want to have a circuit that behaves like it's closed when it's in the receive mode and we want this whole thing to behave like an open when it's in the transmit mode so when we're transmitting at high power this whole thing will appear like an open and when the transmitter is off this whole thing will appear like a short one of the interesting properties of a transmission line a piece of coax that happens to be a quarter wavelength long is that if you short one end of it and then test the other end electrically it will appear to be an open and this is just a property of waves propagating through a transmission line a piece of coax like this so at the frequencies we're interested in for this experiment 3.6 megahertz a quarter wave length of coax would end up being somewhere on the order of 20 meters and so this technique would work you could just coil up 20 meters of coax in there and and this is actually done professionally in NMR Laboratories sometimes but there's an easier way to do it instead of using coax we're going to simulate the piece of coax by using an inductor and a capacitor a parallel capacitance and a series inductance which if you think about it is really what a transmission line is there's a center conductor and there's a whole bunch of capacitance distributed along this thing for so the shield and there's a whole bunch of inductance because it's a wire going through there and so we're going to basically use the equivalent inductance and capacitance of a quarter wavelength of transmission line and the way that you calculate these values is pretty cool so the reactants for both the coil and the capacitor should be 50 ohms and if if we check it out at 3.6 megahertz that's 2.2 micro henries for this and 880 picofarads for the capacitor so now here's where the interesting bit comes in we simulate this quarter wavelength of coax then we put crossed diodes at the end of it so this means that when you have a high power going through here the diodes will be forward conducting and they will essentially act like a short because we've got a huge amount of power coming through here when there's a tiny amount of power coming through it's not enough voltage to forward bias the diodes and they appear not to even be there so in that case the signal just comes right through it doesn't really interact with this at all because we aren't changing the impedance at this point it just sails right through and since the world is so full of non-idealities you actually have to have multiple stages of this to get enough isolation remember we're looking at such a tiny signal and transmitting at such a high power that if you only had one stage of this quarter wavelength with the cross diodes too much signal still gets through potentially even enough to destroy the low noise amplifier but certainly enough to overwhelm it to the point where it won't be usable for another you know a couple milliseconds or in other words our signal is going to be gone by the time the amplifier recovers so we just put stages of this over and over so here's another quarter wavelength and another quarter wavelength and we put cross diodes at every Junction and you can even put more diodes in parallel it doesn't have to be two you could even do four two forward and two backward basically and all this is doing is to increase the isolation make this thing behave even better more performance basically these diodes are 1 and 41 48 so they're very quick and their Junction capacitance is low especially low compared to the 880 picofarads for each one of these quarter Lambda things so that's how the that's how we protect the low noise amplifier and um keep it from being overwhelmed right after a transmit pulse but we still have another problem here even when we aren't transmitting there's a small amount of noise coming out of the transmitter and so as you can see there's a direct path from the output of the power amplifier right into our sensitive circuit and at these low voltage values I mean you know micro volts or Nano volts even we're going to be amplifying in that and that's exactly the range where our signal is going to be so unless the power amplifier is quiet down to the Nano volt level which of course it isn't then this we're completely overwhelmed you're going to be looking at you know all kinds of interference so the last bit of the circuit is an isolator for the transmit side and again we're using cross diodes but now they're in line instead of going to ground and so the idea here is that when we're not transmitting these diodes will not be forward biased and they essentially look like an open when we are transmitting the diodes are forward biased enough to conduct power and it looks like they're a short so it seems like just crossed diodes all by themselves would be enough but we have another problem when the diodes are open when they're not conducting they still have Junction capacitance quite a bit actually it could be as high as I mean large diodes could have a huge amount but even small signal diodes can have five or ten puff of Junction capacitance and guess what that's a problem even at 3.6 megahertz it's enough to get noise or interference from our power amplifier into our Ultra sensitive LNA so what we again have to do this like three stage trick where we're reducing it at each stage and in between the stages we just put a resistor to ground to give a path to drain off more of that interference that we don't want so if we've got a capacitor remember capacitors at AC do have some you know conductance they do pass the signal so then we have to put a resistor and we're basically dividing this dividing the this noise signal or this interference at every one of these stages and I found that three stages of each is enough and it does work actually completely passively with this layout One Challenge is that you have to re-tune the Lambda over four part for every frequency that you want to investigate so at 3.6 megahertz I said the value is you know 2.2 micro Henry and 880 puff but if we switch to 2.5 megahertz or some other frequency to investigate a different material then we have to rewind the toroids and retune this entire thing you have to be careful because if we transmit at the wrong frequency and this quarter Lambda thing is not tuned for the right isolation I mean if we're we don't have the right circuit for the right frequency we can blow out the LNA of course so you got to be careful about that and you do have to spend time retuning unless you have a more advanced technique so while we're talking about tuning let's try to actually do it let's retune the circuit from 3.6 megahertz which was the sodium nitrite frequency and let's change to 2.56 megahertz which should be paracetamol or acetaminophen so what I'm going to do or what I've already done is disconnect the transmitter and receiver and I've connected the Nano VNA to that tuning Port that I have there so the only thing that the Nano VNA is connected to is the matching capacitor the tuning capacitor and the coil and so we're going to change the knobs this is this is the knob for the tuning capacitor this is the knob for the matching capacitor and I'll zoom in so you can see the Nano VNA screen and what to what to expect there okay so here's our circuit currently tuned to 3.6 megahertz and the yellow Trace is showing the return loss going into our setup there so there's a big dip right at 3.6 megahertz because it's absorbing a lot of the energy right at that frequency the green Trace is the Smith chart showing the complex impedance that we're testing at this port and the blue Trace is the Q and it's funny it's actually shown as one divided by the number so the lower the the trace and the blue thing the higher the Q and it currently says that we're about 1 over 0.015 sometimes it's 0.02 so the loaded Q or the Matched Q of that circuit is about 50. so if we turn the tuning capacitor we can very quickly change the resonant frequency and it's very sensitive I'm only turning this thing you know this is about a half turn right here it goes clear across the screen so what we'll do is change the range that we want to get down to 2.56 megahertz so we'll change the start frequency to 2.4 and I'll start turning the tuning capacitor and we're slowly walking the the dip on that yellow Trace down we aren't worrying about the matching capacitor just yet 15.5 that's about 2.56 but as you can see we're not matched very well so one the diff is not very low so we aren't absorbing very much energy the queue actually looks surprisingly good but the Smith chart is also way off so we want to get the green marker so that it's right in the middle of the Smith chart 50 ohms so if I start turning the matching capacitor it makes the green circle bigger we're getting it closer to 50 ohms but now we've detuned the circuit a little bit so it's an iterative process where you're turning both the tuning knob and the matching knob and we want to get 50 ohms right in the middle of the Smith chart at the same time that we're getting as biggest dip possible so let me go back and forth with the knobs here a little bit okay I think that's pretty good we've got uh 48.9 ohms obviously 50 is as good as we can get pretty much and we're right at 2.564 megahertz and the Q is quite High 0.01 over 0.01 even that's just going to be as good as it's going to get also this vacuum variable capacitor was generously donated by Kenneth and it's been sitting on my shelf for years just waiting for its moment so thank you Kenneth Okay so we've got the correct 2.56 megahertz isolation circuit installed we've used the VNA to tune the two capacitors and we have one more thing to do we need to use a magnetic probe to find out what the field strength is inside our coiled air and this will make getting the pulse strength and length correct so this is a a single turn of coax that has the end shorted and a little cut made in the top and you can look up magnetic field probes but I basically have this connected to the green trace on the oscilloscope and what I'm going to do is put the probe right in the coil and then hit the burst button so we just transmitted and I have a measurement set up and it's measuring this length of more or less consistent voltage coming from this probe and it's 2.6 volts which is a bit higher than I want so I'm shooting for a specific power level that will become obvious a little bit later but we're going to turn down the amplitude at which we're transmitting so instead of 240 millivolts let's do 200 and then if we burst again we can see we're getting less magnetic field strength and so the the amplitude that the afg is sending out to the amplifier is just getting boosted by that power amplifier goes through the circuit and creates a magnetic field in that coil and we're measuring the strength of the magnetic field using this magnetic probe we could calculate it but it's much easier to just measure it because then we know what we've got and we're down to about 1.9 volts but we want to be a little bit lower still 1.5 so that's about what we want so I'll put the magnetic probe away and now we'll actually start running the sequence to see if we can see the signal from paracetamol here's our tube filled with the pills we'll just put that in there and then what we'll do so you can see that this is the transmit pulse that we're showing and you can see the pink Trace is what we're getting from the LNA and it's completely overwhelmed from the start of the transmit pulse to about 250 microseconds so what we'll do is just roll all this back so that we're only looking where the thing has stabilized and then hit first now we can see here that we're still getting some of the recovery from the LNA and there's this very Broadband Peak uh that that that's the coil ringing down so what we'll do is slide this a little bit more along and burst again so that we're only inspecting a clean signal and so far we're not seeing anything that could be something I'll start playing with this and averaging it to see if we can get a signal I might have to close the lid too while we're collecting data from the paracetamol let's talk about where this signal actually comes from so imagine we've got an atomic nucleus here and it's got protons and neutrons in there so the net charge is positive recall that there's also this property called spin and the subatomic particles that make up the nucleus each have a spin and they combine together to give a net spin to the nucleus if if there is if for certain materials and remember that if you've got something that's charged and it's spinning that's kind of like a little bar magnet it creates a magnetic field so the nucleus of lots of different atoms is like a little bar magnet and if we were to put this in an electric field it would not really try to rotate because it's a magnet it's not electrically it doesn't have an electric moment but if we put it into a magnetic field then it would align just like we have these Compass needles are aligned with the Earth's magnetic field same thing so I'll show you another property that's going to be relevant here I've got this toy gyroscope that I'm going to spin up and if we hold it vertically not much happens but if we tilt it and then let go it precesses and so gravity is trying to pull it down pull it straight and the gyroscope precesses in response right I mean that's that's what these gyroscopes do and this is another property that the atomic nucleus has and so it's like a bar magnet but it also has this gyromagnetic quality and the rate that this thing precesses is another interesting thing it's partially due to gravity so if we were to take this same gyroscope to Jupiter or the Moon it would precess at a different rate because gravity would be exerting a different force on it and so the same thing happens in an MRI machine the strength of that magnet causes these nuclei to align with it and if you do something to perturb the direction of these little magnets the little nuclei they precess at a specific rate as they try to realign with the magnetic field and that rate of precession is determined by the big magnetic field in an MRI machine okay so if we were going to use this in a system we need a couple things we need one way to determine if the atomic nuclei are are processing like the gyroscope was so when they're twirling around like this we need some way of detecting that that's relatively straightforward that's just a coil of wire so if we put a coil of wire around all these Atomic nuclei and amplify what's coming back we can sense when they're all spinning around in unison when they're all precessing in unison because they create a very tiny magnetic field that we can pick up with a coil of wire a little bit more challenging is how do we process them how do we get them processing in unison in the first place you might think well great we'll just transmit a really powerful pulse and really blast them into orbit but unfortunately it doesn't work that way there's actually a sweet spot where we have to get them processing at maximum velocity and if we go too far with the transmit pulse in terms of power or time then we actually blow past The Sweet Spot and don't get any signal let me show you why okay so imagine this is our Magnetic Moment here and our nuclei is in there and it's perfectly aligned so that it's not precessing right now we haven't perturbed it yet and everything is perfectly aligned so now we start giving it a transmit pulse and we start to cause this thing to process by transmitting at the characteristic frequency now if we just Freeze Frame it right here we can see that the angle that it's making there is an angle between the resting field and the axis of this procession and remember it's always twirling around like this but we can always Freeze Frame it at the extremum and measure this angle that it's making this is called the flip angle so if we transmit for a long period of time it will absorb more and more energy and flip further and further out until it's 90. in fact it keeps going all the way to 180 degrees so as long as we're transmitting we're causing this thing to change its flip angle and this is why it has a sweet spot so if we transmit for just the right amount of time and flip it by 90 degrees now the thing is twirling like this and we're getting a lot of signal out of it so that's good if we transmit for 180 degrees and twirl this thing all the way around and let go now we get exactly zero signal out of it so this is The Sweet Spot I was talking about you always want to shoot for 90 degree flip angle to get the maximum amount of of precession and the maximum amount of signal out and as it turns out the flip angle is just the product of the transmit power and the time that you're transmitting so you can double the power and have the time and it's exactly the same flip angle this is why I wanted to measure the magnetic field that's happening inside our coil so that we know what the transmit strength is and then we can calculate the correct time to transmit to get a 90 degree flip now hold on you're probably saying this might all be fine for MRI machines with giant magnets but how is this working without any magnet yeah so that's that's the exciting bit so this so far we've been talking about nuclear magnetic resonance which is the thing that MRI machines use to make an image but as it turns out some Atomic nuclei do not have the charge distributed evenly they're kind of oval shaped or oblate like this right so they not only have a magnetic moment they also have an electric moment because the charge is just not spherical right like it's it's still positive it's still positives and um and neutrals in the in the nucleus but they're just spread out like this so that if we did put this into an electric field it would actually have a tendency to align so the next great question is where does the electric field come from we don't have that either all we have is a coil of wire what's interesting is the electric field comes from the molecule itself so these nuclei are let's say this is nitrogen it's if nitrogen is part of a bigger molecule there's other things around it in the molecular crystal structure that also have charge so much further away I mean if this was drawn to scale it'd be ridiculous but nearby atoms and nearby other molecular structures will have a charge and this thing will basically be in an electric field all the time just because it's in a molecule um you can actually see this property very easily just charge up a comb or a piece of plastic and hold it near a stream of water the water will completely Bend out of the way because its molecules have very strong positive and negative sections to them it's a polar molecule and so most molecules have not perfectly even charged distribution and that's how we can take advantage of all this now one downside is that these oblate type nuclei are not particularly common luckily nitrogen is one of them and chlorine is another one but if your substance doesn't have either nitrogen or chlorine in it this method will not be particularly helpful but on the upside lots of times we want to find things that have nitrogen in it for example Pharmaceuticals and explosives are two categories of things that very often have nitrogen they have this oblate thing and then we can use this technique called nuclear quadrupole resonance nqr I've said a few times but that's what it stands for so quadrupole is this shape of the nucleus that has an electrical non-uniform distribution but there's another problem in an MRI machine the magnetic field is the same everywhere so every nucleus is experiencing the same magnetic field but in this idea of nqr where we're actually using the electric field of the local crystalline structure imagine you've got a sample like this that's you know powder basically or small crystals that means each location is going to be oriented completely different how could we ever get a signal out of this but yeah it's true that that is a problem and that is one of the reasons why nqr has such terribly weak signals it's nothing compared to an MRI machine but it does work there is one slight concession so if you think that the ideal flip angle should be 90 degrees because then you get the biggest precession in nqr with a powder sample it turns out that the ideal flip angle is about 110 or 120 degrees to compensate for the fact that all of the crystals are oriented randomly in there and the ones that are upside down don't subtract from the signal it's just luckily it doesn't matter if it's aligned up or down with the magnetic field or the electric field so being upside down doesn't cancel us out but being sideways makes the signal very weak so we do end up losing a lot of signal to a powder sample I've got one more trick that I know you're gonna like so far we've been talking about these 90 degree pulses and it seems like yes this is the best way to get signal out if it's starting off like this we tip it 90 or 110 or 120 degrees to get the maximum amount of precession which is what we pick up with the coil but this does have a problem and here's what it looks like if our transmit pulse is here and we call this a 90 degree pulse because it's of the right amplitude and the right time to tip this thing from vertical or from aligned with the field to 90 degrees and that gives us a good signal so the receive Channel looks like this where we get a signal and then it kind of dies out the reason that it dies out at first seems like it's because this thing is precessing and then it's slowly realigns with the field that's around it but that's actually not the case the reason that the signal dies out is because throughout the material there's like micro tiny variations in the procession speed for each nucleus and this has to do with like you know ultra microscopic temperature variations throughout the material it has nothing to do with keeping the material at the same temperature this is like you know thermodynamic variations that you just can't get rid of and because of this if this guy is going a little bit faster than the one on this side they will become out of phase and as soon as these things are processing in different ways we lose all of our signal if if some of them are going faster than others the signal will decay and the time it takes to Decay because of the fact that some of the nuclei are going faster than others is called the t2 star time and for the sodium nitrite sample that we looked at today that time is on the order of two or 300 microseconds and so that's very short and this is bad because we we really need to switch from transmit to receive very quickly and then we're losing the best part of the signal because it's high amplitude and then dies down but if we can only start receiving here then we've lost the best part of the signal so we need to figure out a way to get around this and there's a super clever technique check this out now we're talking about multi-pulse multi pulse pulse sequences so instead of just doing one 90 degree pulse we're going to do two pulses and this is actually going to give us a much better signal so here's the idea we first start with the aligned the aligned nuclei and tip it 90 degrees so now we're getting a pretty good signal we could record it if we want but we we probably won't and then we wait a little while the Signal's gone because of this dephasing effect then we give it a 180 degree pulse so that now the ones that were spinning you know clockwise are spinning counterclockwise and we wait a little while longer and we suddenly get this Echo a much bigger signal and much farther away from our transmit pulse so that we have time to recover and record the whole thing and here's the way to think about this imagine there's a foot race a whole bunch of people are lined up on a starting line you start the race some people are faster than others so they pull ahead they all run at the same speed each runs at their own speed instead of having them cross the finish line all at different times we stop them all at one instant halfway through the race and tell them to go back towards the starting line So the faster ones have covered more distance but they're running faster so when they turn around and go back towards the starting line they will get there at exactly the same time as the slower Runners so all the nuclei throughout the entire sample have all these different speeds going on and the fact that we give it a 180 degree pulse means that we compensate for that fact because we've switched the direction and we create this rephasing so that slowly they become back into phase and give us a maximum signal and then dive back out again but here's the thing we can give it another 180 degree pulse and re-phase them again and again and again and you can easily do 10 or 20 re-phasings the only thing that limits you is it's true that as we're flipping this thing back and forth 180 degrees eventually we are in fact running out of of flip angle of total angle from thing and once it aligns again with the field we can't really flip it 180 degrees anymore because now it's not processing so the time it takes for this thing to really run out of gas is called the T1 time and it's much much longer than this so-called T2 star time anyway I just thought that's a really clever trick I haven't gotten this to work at all on my setup I haven't even attempted it yet but maybe a good one for a follow-up video okay so now let's have like the one minute intro to Quantum Mechanics so far we've been talking about this in classical terms of spinning and flipping and gyroscopes and stuff but there's a completely parallel way to think about how all this is working the idea is that when you put a um a nucleus into a magnetic field or a quadrupole into an electric field some of them will align with the field and some will be upside down and this is the funny thing it's not really like a bar magnet obviously all of these Compass needles are aligned with the Earth's magnetic field north to south but the thing with a spinning nucleus is it's not like that sometimes they align that way and sometimes they align that way and it's about half and half when you put these into a magnetic field or an electric field and the idea is that the energy level between these two is very slightly different and the stronger the field the bigger the difference in energy so sometimes you'll see it written on a diagram like this where it splits out into two and the idea is that you started with the same energy for both um or you started with the same energy because none of them had any particular orientation but when you put it into a field you split the energy levels because some will align and some will be anti-aligned and if you measure the difference in energy between the high energy State and the low energy State and you put all of that energy into a photon the frequency of that Photon would be exactly the same as the frequency of the procession that we were talking about that's kind of a nice mind blow right like it ties all this together and this is actually this idea of splitting something into two energy levels is known as xamon splitting and it's exactly the same xamon phenomenon that I showed in an earlier video that will affect Optical absorption spectra same exact idea magnetic field changes the atomic properties based on splitting this energy level and it's also the same thing that we use to calibrate atomic clocks as shown by a curious mark so here's the setup I ended up with for the paracetamol or the Tylenol I ended up using a much larger area or a much larger volume of sample and still have got kind of inconclusive results it's a real weak signal that's not very repeatable so it's possible there's going to be some follow-up videos and as always put questions in the comments and I'll you know answer them either next time or in the comments so anyway I I think there'll probably be more to talk about but I hope you found that interesting and I'll see you next time bye

Channel: Applied Science

Views: 431,409

Keywords:

Id: JO_EHceV9sk

Length: 37min 3sec (2223 seconds)

Published: Sun Jan 22 2023