Deep UV resonance Raman spectroscopic study of CnF2n+2 molecules: the excitation of C-C σ bond

The sigma-sigma* transition of CC bond in CnF2n+2 molecules was studied by deep UV resonance Raman spectroscopy. With the CC s bond selectively excited by the deep UV laser at 177.3 nm, the resonance Raman spectra of CnF2n+2 molecules were obtained on our home-assembled deep UV Raman spectrograph. The Raman bands at 1299, 1380 and 2586 cm-1 due to the CC skeletal stretching modes are evidently enhanced owing to the resonance Raman effect. Based on the resonance Raman spectra and theoretical calculation results, it is proposed that the electronic geometry of CnF2n+2 molecules at the ss* excited state is displaced along the directions perpendicular and parallel to the CC skeleton, and the excited CC bond is not dissociative due to the delocalization of the excited electron in sigma* orbital. Copyright (C) 2012 John Wiley & Sons, Ltd.