Vibrational dynamics of the linear and bent isomers of HF–N2O trapped in 0.4K helium nanodroplets

Infrared (IR)–IR double resonance spectroscopy is used to probe the isomerization dynamics of helium solvated HF–N2O following the vibrational excitation of one of two stable isomers on the intermolecular potential energy landscape. An upstream pump laser excites the H–F stretching fundamental of either the linear ONN–HF or the bent NNO–HF isomer, while a downstream probe laser is scanned through the bands of both isomers to test for photo-induced isomerization. Vibrational excitation of the H–F stretch mode leads to the isomerization of a fraction of the upstream population, regardless of the identity of the pumped isomer. The measured isomer interconversion is consistent with vibrational predissociation followed by geminate recombination. A fraction of the upstream population is unaccounted for by the downstream probe. We propose that a fraction of the missing population is due to the mismatch in the timescales of complex recombination and pump, probe events.