It was recalled that the B-H complex could be aligned by stress, and reoriented with an activation energy of about 0.2eV. Here, new measurements of the reorientational kinetics of the B-H complex (obtained by using the stress-induced dichroism technique) were combined with previous internal friction results in order to show that the reorientation kinetics were non-Arrhenius in nature. These results supported the suggestion that reorientation occurred via thermally assisted tunnelling. It was also discovered that the reorientation rate of B-D was greater than that of B-H, at temperatures above 57K.

Y.M.Cheng, M.Stavola: Physical Review Letters, 1994, 73[25], 3419-22