Physical chemistryLesson 2 of 2 in the course Magnetic resonance imaging

Nuclear Magnetic Resonance: Spin, Spectroscopy, Relaxation, and Applications

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

This lesson introduces the nuclear properties that make NMR possible. Understanding nuclear spin and magnetic moments explains why some isotopes produce signals while others do not.

Atomic nuclei contain protons and neutrons, collectively called nucleons. Nucleons possess intrinsic angular momentum, or spin. The total nuclear spin is represented by the quantum number SS (often written as II in NMR conventions).

All flashcards

Gyromagnetic ratio
The proportionality factor relating a nucleus's spin angular momentum to its magnetic dipole moment.
RF pulse
A brief radiofrequency magnetic field that perturbs nuclear magnetization; its duration and strength determine the resulting flip angle.
T1T_1 relaxation
The return of longitudinal magnetization toward thermal equilibrium through recovery of spin populations.
Hahn echo
A signal-refocusing method using a 90-degree pulse followed by a 180-degree pulse after a delay.
Radiation damping
Feedback in which current induced in the receiver coil creates a field that acts back on the sample.

Quiz questions

  1. How does FT-NMR acquire a spectrum?Answer: A short RF pulse excites many frequencies, and a Fourier transform converts the resulting FID into a spectrum.
  2. What is the typical effect of greater electron shielding on a nucleus's resonance position?Answer: It reduces the effective field and shifts the resonance upfield, to a lower chemical shift.
  3. What does T1T_1 relaxation describe?Answer: Recovery of longitudinal magnetization toward thermal equilibrium.
  4. Why is magic angle spinning used in solid-state NMR?Answer: Rotating the sample near 54.74 degrees averages important orientation-dependent interactions.
  5. What type of information can zero-field NMR provide when chemical shifts no longer dominate?Answer: Field-independent spin-spin coupling information.

Based on the Wikipedia article Nuclear magnetic resonance, licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.

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