Spectroscopy and photophysics of the CF 2[formula omitted] system

Abstract

Laser excited single vibronic level (SVL) fluorescence and SVL fluorescence excitation spectra of the low pressure vapor phase CF 2 A ̃ - X ̃ transition are reported. The spectral origin is at 268.74 nm (37 197 cm −1); extensive progressions in the bending mode ν″ 2 = 666 ± 5 cm −1 dominate the spectra; weaker combination bands involving the symmetric stretch ν″ 1 = 1186 ± 15 cm −1 are observed. Fluorescence bands appear that may be assigned as originating either from the 1 12 n or the 2 n 3 1 vibronic levels, giving ν′ 1 = 976 ± 24 cm −1 or ν′ 3 = 900 ± 20 cm −1, respectively. Measured vibronic band intensities 〈 v′| v″〉 2 are given for all transitions from the upper states 2 n for 0 ≤ n′ 2 ≤ 6. The collision-free A ̃ (0,0,0) state radiative lifetime is 61 ± 3 nsec. This same lifetime is observed even for vibronic states containing 8000 cm −1 excess vibrational energy (i.e., the n′ 2 = 16 level). SVL fluorescence spectra and radiative lifetimes were used to calculate the transition dipole moment R ̃ e = 1.22 D for this system, and a low resolution absorption cross section σ(2 0 0; 300 K) = 6.7 × 10 −19 cm 2 for the A ̃ - X ̃ origin at band maximum (268.74 nm).