Zeeman relaxation of CaF in low-temperature collisions with helium

The collision-induced Zeeman relaxation rate for collisions of CaF X-2 Sigma(v '' = 0) with He-3 is measured to be Gamma(Z) = (7.7+5.4/-2.5) x 10(-15) cm(3)/s at 2 K. This rate is a direct measurement of the influence of spin-rotation coupling on Zeeman relaxation in the first rotational level of CaF. The relationship of this rate to known molecular constants is consistent with recent theory of cold molecular collisions and outlines the (2)Sigma molecules conducive to magnetic trapping.