Novel temperature dependence of the vibrational relaxation of SH− in a two-state hopping system

Vibrational saturation measurements of the SH− molecule doped in KBr are performed from 1.7 to 78 K. If a single relaxation time is fit to the saturation curves, it is found to increase with increasing temperature, in contrast to theoretical expectations. However, KBr:SH− has recently been shown to possess two distinct elastic configurations between which interconfigurational hopping has been identified. If the vibrational lifetimes are different in these two states, an increasing effective decay time for the system as a whole can be obtained even when the two individual times remain constant or even decrease with rising temperature.