Gas phase electronic spectra of two C5H5 radical isomers

Abstract

Gas phase electronic spectra of two C₅H₅ radical isomers have been observed in the 440–470 nm spectral region. The technique was a mass selective resonant two-color two-photon ionization coupled to a supersonic plasma source. Structures, relative energies and vertical electronic transition energies of six isomers of C₅H₅ have been calculated. Based on an analysis of the rotational profiles of the observed bands and theoretical calculations, the spectra are assigned as the à ²A″ ← ²A″ electronic transition of isomer 1 and à ²A₂ ← ²B₁ of 6 with origin band at 461.8 nm and 456.1 nm, respectively. Isomer 1, 1,3-vinylpropargyl, has C_s symmetry, while 6, a planar zig-zig chain with one hydrogen on each carbon, has C_2v symmetry.