The 291-nm band system of 3-fluorostyrene: Gas-phase absorption and single vibronic level fluorescence spectra

Abstract

The Ã1A′-X̃1A′, 291-nm system of 3-fluorostyrene has been studied in the gas phase by means of the absorption spectrum and also single vibronic level fluorescence (SVLF) spectra. The absorption spectrum is dominated by the cis rotamer but a few bands of trans are also observed. The cis spectrum resembles that of styrene rather closely showing many hot bands, in the region of the 000 band, which involve ν42, the C(1)-C(α) torsional vibration, and ν41, the out-of-plane bend about C(1). The 41014210 cross-sequence band is prominent. SVLF spectra with excitation in the 000 and 41014210 bands show progressions in ν″42 with v″42 even and odd, respectively, giving the first six torsional levels of the cis rotamer. Rotational band contour calculations show that the 000 bands are predominantly type A but that it is not possible to distinguish contours of the cis and trans rotamers in this way.