| Abstract: | The electron paramagnetic resonance (EPR) spectrum of an asymmetric interstitial H centre in LiF has been studied as a function of temperature. The shifts with temperature of the EPR lines have been measured from 7 to 150 K. They are interpreted by a libration process of the molecule ion around its mean orientation. Near 180 K, the EPR lines broaden. The thermally activated broadening arises out from reorientational motions of the molecule ion. The reorientation rates show that there are two distinct jumping motions between 180 and 230 K; one of them implies rotations of the molecule ion around the average 〈111〉 orientation and is assumed to be induced by the same librations modes as those which produce the line-shifts. The other one is the pyramidal jumping motion between the four equivalent 〈111〉 orientations. |
