Vibronic spectra, ab initio calculations, and structures of conformationally non-rigid molecules of oxalyl halides in the ground and lowest excited electronic states. Part IV: Analysis of the absorption spectra of oxalyl fluoride in the gas phase

Abstract

The gas phase absorption spectrum of oxalyl fluoride in the region of 37 000–29 300 cm −1 has been examined at high resolution. Singlet–singlet A ˜ 1 A u ← X ˜ 1 A g and singlet–triplet a ˜ 3 A u ← X ˜ 1 A g electronic transitions of the trans-conformer were found in the spectrum. The fundamental frequencies of trans-oxalyl fluoride in the A ˜ 1 A u and a ˜ 3 A u electronic states were determined. In the low resolution ultraviolet absorption spectrum of oxalyl fluoride in the gas phase the A ˜ 1 B 1 ← X ˜ 1 A 1 transition of the cis-conformer ( ν max) was found to be shifted to the blue by about 6000 cm −1 relative to the A ˜ 1 A u ← X ˜ 1 A g transition of the trans-conformer.