Visible electronic absorption spectrum of vinyl radical

Abstract

A simple, banded absorption spectrum has been detected by photochemical modulation spectroscopy in Hg-photosensitized reactions forming vinyl radicals. It starts at 499.5 nm, reaches maximum intensity ε ≈ 30 M −1 cm −1 around 400 nm, and contains progressions of 1200 and 920 cm −1 vibrations. These features are compatible with the electronic structure, equilibrium geometries, and energies of the 2 A′ ground and 2 A″ first excited states of vinyl which were determined by abinitio SCF calculations. The upper state of the observed transition is analogous to the [Formula: see text] state of the isoelectronic formyl radical.