Cross relaxation dispersion and temperature dependence of nuclear spin dipolar and rotating frame Zeeman energies: A study of ammonium halides

The less known properties of cross relaxation between detectable spins I and fast relaxing spins S, such as the two types of H1 dispersion and the occurrence of two minima of the rotating frame Zeeman relaxation time T1x(I), when γH1T1(S)min<1, or the occurrence of two minima of the dipolar relaxation time T1d(I), when γHL, eff(I) T1(S)min<1 and T1(S)min≪T2(IS), are briefly discussed in the framework of the Blinc–Pirs–Žumer theory. The experimental results on cross relaxation between detectable spins I (protons or deuterons) and fast relaxation spins S (bromine, iodine, and chlorine) in the cubic phases of solid NH4Br, NH4I, and NH4Cl, and their deuterated analogs, are presented and explained.