A new technique for state-to-state studies of unimolecular reactions

Abstract

A double‐resonance technique which combines infrared excitation of a fundamental vibration of a light atom oscillator with vibrational overtone excitation of that same oscillator selectively prepares molecules in individual quasibound vibrational–rotational states at energies above their dissociation threshold. A third laser probes individual states of the product fragments via laser induced fluorescence. We present our initial results applying this technique to study the 6ν_OH vibrational overtone spectroscopy and unimolecular dissociation dynamics of hydrogen peroxide (HOOH). The double‐resonance approach simplifies the congested vibrational overtone spectrum of HOOH, and the linewidth of resolved features places a lower limit on the lifetime of approximately 7 ps.