Rotational analyses of bands of the system of cis-glyoxal

Abstract

Rotational analyses have been carried out for the 510, 501, and 511 bands of the [Formula: see text] system of cis-glyoxal, where ν5 is the totally symmetric C—C=O bending frequency. The vibrational frequencies [Formula: see text] and [Formula: see text] are smaller than the corresponding frequencies for trans-glyoxal by nearly a factor of two. A vibronically induced band with a different type of rotational structure has been analysed and shown to be an a-type band. The coupling vibration is the out-of-plane C—H wagging vibration ν6(a2) and is similar in form and frequency to the vibronically active ν8(bg) vibration for trans-glyoxal.