А из такой фразы :
Цитата
The nuclear spins of the atoms in the examination subject are excited by means of these radio-frequency pulses such that they are deflected from their equilibrium state (parallel to the basic magnetic field B0 ) by what is known as an "excitation flip angle" (generally also called a "flip angle"). The nuclear spins then precess around the direction of the basic magnetic field B0.
можно предположить , что flip angle distribution есть распределение углов прецесси спинов .