Observation of Coriolis Coupling between ν2 + 4ν4 and 7ν4 in Acetylene X̃1Σ+g by Stimulated Emission Pumping Spectroscopy

Abstract

Stimulated emission pumping (SEP) spectroscopy has been used to examine a low energy region (Evib ≈ 4400 cm−1) of X̃1Σ+g acetylene at higher resolution than was possible in previous dispersed fluorescence studies. The expected bright state, ν2 + 4ν4, is observed to be coupled to the nearly degenerate 7ν4 state by a Coriolis mechanism. A least-squares analysis yields values for zero-order vibrational energies, rotational constants, and a Coriolis-coupling coefficient that are all consistent with expectations. Calculated relative intensities of SEP transitions, accounting for interference due to axis-switching effects, are also consistent with observations. Implications of the observed Coriolis resonance with regard to global acetylene vibrational dynamics are also discussed.