Nuclear Spin Relaxation in Cs and Rb Metals below 77°K

Experimental values of the product T₁T have been determined in the low-temperature range for the nuclear spin systems Cs¹³³ and Rb⁸⁷ in Cs and Rb metals. Anomalous results previously reported for Cs at low temperatures have been shown to arise from thermal gradients in experimental samples and are spurious. The experimental values which obtain from 1.4 to 77^∘{}K are T₁T=0.13±0.01 sec^∘{}K for Cs¹³³ and T₁T=0.11±0.01 sec^∘{}K for Rb⁸⁷. Spin-echo measurements of the intrinsic T₂ for Cs¹³³ in our samples give T₂=1.5 msec. This number agrees with determination of intrinsic linewidths by others by independent techniques.