Spin Echo Modulation Caused by the Quadrupole Interaction and Multiple Spin Echoes

Abstract

A spin echo amplitude for a spin system consisting of one nuclear species of spin I with a large Zeeman energy and a small quadrupole interaction has been calculated for the case the excitation is carried out by two succeeding arbitrary rf pulses. The spin echo amplitude shows an oscillatory behavior which depends on the time interval between the first and the second pulses. The relation between this fundamental modulation period and the separation of the multiplet of steady state NMR absorption signal is derived. The possibility of observing multiple spin echoes is discussed and the modulation periods of these multiple echoes are calculated. These results showed satisfactory agreement with the experimental results observed on boron nuclei in ferromagnetic Fe 2 B and MnB and on manganese nuclei in ferromagnetic MnB.