Spectral effects of ultrafast barrier crossing in a two well potential

MD simulations for a triatomic molecule, in Ar solution, where the central atom moves in a double well potential were performed. The IR spectra of the molecules gave clear evidence of the effect of increasing barrier to the reaction: at low barrier height the signals of the two isomers are merged together and then separate increasingly as the barrier height is increased. The spectra could be fitted by Bloch lineshapes but the parameters obtained in this way were not sufficiently well defined to be of value. Barriers estimated from the temperature dependence of the lifetimes agreed well with those obtained from the bare potential indicating effective shielding of the reaction coordinate from the solvent.