IR–IR double resonance spectroscopy in helium nanodroplets: Photo-induced isomerization

Abstract

Two IR lasers are used in a pump–probe configuration to observe photo-induced isomerization between the linear and bent isomers of HCN–HF, formed in helium nanodroplets. Vibrational excitation of the C–H and H–F stretching modes of these complexes provides sufficient energy to surmount the barriers between them. The extent of population transfer is found to be different for pumping the two isomers. In the case of linear HCN–HF, the results suggest that the complex undergoes vibrational predissociation, followed by geminate recombination. Excitation of the higher energy bent HF–HCN isomer results in complete population transfer to the linear complex. This isomer specific population transfer provides important clues regarding the associated vibrational dynamics.