Magnetic-resonance studies of negative ions in liquid He3-He4 mixtures

This paper reports an extensive experimental study of the ESR signals from negative ions in pure He3 and in He3-He4 liquid mixtures. The first determination of the spin-lattice relaxation time, T1, for these ions in He3 and He3-He4 is presented. We have measured T1 as a function of pressure, temperature, and He3 concentration. The g value of the negative ion was found to be pressure, isotopic concentration, and temperature independent, and equal to the free-electron g value. Attempts were made to observe electron-nuclear double-resonance phenomenon (ENDOR and dynamic nuclear polarization), but none were observed. A theoretical calculation of T1 as a function of pressure and isotopic concentration was carried out. Reasonable agreement between these theoretical estimates and the observed T1 was obtained.