Pulse techiques in NMR
Start with the big picture
An RF pulse tips net magnetization away from the +z axis, with its flip angle determined by pulse duration and power. A 90° pulse brings magnetization into the xy-plane and initiates the observable free induction decay (FID); a 180° pulse can invert spins or refocus dephasing. Sequence timing gives these pulses different roles: spin–echo experiments measure T₂ while addressing static field inhomogeneities, and inversion-recovery experiments map longitudinal recovery to quantify T₁. Other techniques process or shape the signal: Fourier transformation converts the FID into a frequency spectrum, while phase cycling and quadrature detection support signal selection and frequency discrimination. Selective, composite, adiabatic, decoupling, gradient, and spin-locking approaches extend pulse control to spectral editing, coherence selection, and additional relaxation information.
What you'll learn
- Explain how RF pulses tip net magnetization and define experiment timing.
- Distinguish the roles of 90° and 180° pulses.
- Describe how spin–echo and inversion-recovery sequences relate to T₂ and T₁ measurements.
- Identify how signal processing and pulse techniques support spectral selection and correlation.
- Recognize the purposes of selective, composite, adiabatic, gradient, and spin-locking methods.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
