NMR and NQR
Equiped with your new knowledge about orientation, temperature and radiation absorption, you are ready now to understand NMR and NQR — two methods that make use of these properties:
If you want to read more/other explanations about NMR/NQR, then these are two optional resources:
- a good basic explanation from a chemistry point of view
- chapter 4 of this book (chapter written by Brunklaus, Spiess and Eckert)
- We have been mainly concerned by the physics application of NMR, also called MRS or Magnetic Resonance Spectroscopy. It’s main goal is to detect the presence of (small) quantities of various kinds of molecules via the chemical shift. For medical applications (MRI), the goal is different: creating images. That requires in the first place spatial localization techniques (gradient coils) and pulsed signals to distinguish the gross features of e.g. water and fat from each other. We only touched slightly on MRI in this course. If you want to dig deeper into MRI, a very useful site is MRIquestions.com. It discusses the physics background, the medical technique, the tools involved, and much more. You do have right now the basic knowledge required to digest that source.
There are four questions related to this topic. The first two of them require a little algebra. You can type your answers, or write them by hand and scan to pdf (preferably compress it). Upload these two answers as one single pdf file (not zipped, not tarred,…) via this ‘quiz’ button underneath:
The other two questions should be answered directly in the form.
Here they are:
To be answered by uploading one pdf file:
- [1] For a nucleus with I=1/2 and a g-factor of 2, and for an applied field of 4 T, which frequency of rf-field do you need to achieve the resonance condition? Indicate where this ends up in the electromagnetic spectrum.
- [2] You have a NMR spectrometer in your lab which generates an applied field of 2.4 T. You measure that the TMS reference sample resonates at a rf-frequency of 102.14 MHz in this machine. If you then measure in another sample a resonance with a chemical shift of 1.23 ppm w.r.t. TMS, calculate:
- [A] what the resonance frequency for protons in that environment is.
- [B] how much the induced field (in T) deviates from the induced field in TMS.
Expected time: 1h15 minutes (report)
B09-03