Phase lag in the amplitude modulated magnetic resonance
Response of a magnetic spin system to the amplitude modulated radiofrequency field is studied. Spin system is assumed to obey Bloch equations. For a spin system resonant at Larmor frequency coo, calculations demonstrate how the phase lags Phi (perpendicular to) and Phi (z), of magnetization components M-x, M-y and M-z occur and how sensitive they are to the relaxation properties of the system. Relative to Larmor frequency the angular frequency of the amplitude modulation. Omega much less than omega (0), is very low, at the same time it is comparable to the relaxation rates of the spins. With reference to the analytical solution of a damped harmonic oscillator a simple formula tan Phi (perpendicular to) = T-2 Omega describes the magnitude of the phase lag Phi (perpendicular to) as a function of relaxation time T-2. (C) 2001 Elsevier Science B.V. All rights reserved.
phase lag amplitude modulation magnetic resonance magnetization spin system relaxation