DIPOLAR ZEEMAN MIXING IN WEAK MAGNETIC-FIELDS - AN EXPERIMENT WITH ICE PROTONS

The evolution of the longitudinal magnetization of nuclear spins in a cw high-frequency magnetic field has been measured using a SQUID magne tometer at liquid-helium temperatures in magnetic fields H-0 of up to 57 Oe. The time T-m for thermal mixing of the Zeeman and dipolar syste ms has been found to range between 0.05 and 4x10(2) s. For T-m>1 s the function T-m (H-0) is exponential. The proton NMR spectra near the fu ndamental and twice the Larmor frequency have been obtained. The shift in the resonance with respect to the Larmor frequency is close to the theoretical prediction. (C) 1998 American Institute of Physics. [S106 3-7761(98)01709-0].