= Nuclear magnetic resonance
{tag=Tomography}
{wiki}
= NMR
{c}
{synonym}
{title2}
<Ciro Santilli> once visited the chemistry department of a world leading university, and the chemists there were obsessed with <NMR>. They had small benchtop <NMR> machines. They had larger machines. They had a room full of huge machines. They had them in corridors and on desk tops. Chemists really love that stuff. More precisely, these are used for <NMR spectroscopy>, which helps identify what a sample is made of.
Basically measures the concentration of certain isotopes in a region of space.
\Video[https://www.youtube.com/watch?v=e-vSNPW1NO0]
{title=Introduction to NMR by Allery Chemistry}
{description=
* only works with an odd number of <nucleons>
* apply strong <magnetic field>, this separates the energy of up and down spins. Most spins align with field.
* send <radio waves> into sample to make nucleons go to upper energy level. We can see that the energy difference is small since we are talking about radio waves, low frequency.
* when nucleon goes back down, it re-emits radio waves, and we detect that. TODO: how do we not get that confused with the input wave, which is presumably at the same frequency? It appears to send pulses, and then wait for the response.
}
\Video[https://www.youtube.com/watch?v=873nDYqyWok]
{title=How to Prepare and Run a NMR Sample by University of Bath (2017)}
{description=This is a more direct howto, cool to see. Uses a <Bruker Corporation> 300. They have a robotic arm add-on. Shows spectrum on computer screen at the end. Shame no molecule identification after that!}
\Video[https://www.youtube.com/watch?v=uNM801B9Y84]
{title=Proton Nuclear Magnetic Resonance by Royal Society Of Chemistry (2008)}
{description=
This video has the merit of showing real equipment usage, including <sample preparation>.
Says clearly that NMR is the most important way to identify <organic compounds>.
* https://youtu.be/uNM801B9Y84?t=41 lists some of the most common targets, including <hydrogen> and <carbon-13>
* https://youtu.be/uNM801B9Y84?t=124 <ethanol> example
* https://youtu.be/uNM801B9Y84?t=251 they use solvents where all <protium> is replaced by <deuterium> to not affect results. Genius.
* https://youtu.be/uNM801B9Y84?t=354 usually they do 16 <radio wave> pulses
}
\Video[https://www.youtube.com/watch?v=7aRKAXD4dAg]
{title=Introductory <NMR> & <MRI>: Video 01 by Magritek (2009)}
{description=<Precession> and <Resonance>. Precession has a natural frequency for any angle of the wheel.}
\Video[https://www.youtube.com/watch?v=jUKdVBpCLHM]
{title=Introductory <NMR> & <MRI>: Video 02 by Magritek (2009)}
{description=The influence of <temperature> on spin statistics. At 300K, the number of up and down spins are very similar. As you reduce temperature, we get more and more on lower energy state.}
\Video[https://www.youtube.com/watch?v=GjLvu1hOAAA]
{title=Introductory <NMR> & <MRI>: Video 03 by Magritek (2009)}
{description=The influence of <temperature> on spin statistics. At 300K, the number of up and down spins are very similar. As you reduce temperature, we get more and more on lower energy state.}
\Video[https://www.youtube.com/watch?v=RZLew6Ff-JE]
{title=<NMR> spectroscopy visualized by ScienceSketch}
{description=2020. Decent explanation with animation. Could go into a bit more numbers, but OK.}
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