Proton Magnetic Resonance in LiquidIso-Butyl Bromide

Abstract

Proton magnetic resonance relaxation times T1 and T2 in liquid iso-butyl bromide [(CH3)2 CHCH2Br] have been measured at 21.5 × 106 c/s over the temperature range 110°K to 330°K. The results, together with others for T2 down to 90°K, are interpreted in terms of molecular motion of the molecule as a whole and of the methyl groups in it. This extremely wide temperature range without phase transitions allows a severe test of the validity of theories of nuclear relaxation in molecular substances. The correlation frequency as a function of temperature which ranges from 102c/s to 1011c/s is deduced and a remarkably good correlation with dielectric loss measurements is found. A distribution of correlation frequenices of molecular reorientation at low temperatures is confirmed and the effect of the more rapid reorientation of one methyl group is found. This is a case in which the nuclear resonance parameters are controlled principally by the motion of the molecule as a whole but are modified by an internal molecular motion which is considerably faster.