A reanalysis of the Ã A1″−X̃ A1′ transition of CFBr

Abstract

The laser induced fluorescence spectrum of the A (1)A(")-X (1)A(') transition of CFBr is presented, with selected bands recorded at sub-Doppler resolution, allowing the rotational constants to be fully determined. Analysis of dispersed fluorescence spectra and the pattern of (79)Br/(81)Br isotope splittings indicate that the origin must be shifted from previous assignments in the literature to 23 271.0 cm(-1). This implies that only the lowest four vibrational levels in the A state have significant quantum yields for fluorescence, with all other levels strongly predissociated. Comparison with photofragment measurements implies that the A state is metastable, with a barrier to dissociation of approximately 1000 cm(-1).

All-Electron Relativistic Multireference Configuration Interaction Investigation of Fluoroiodo Carbene

“…It has been indicated that the dissociation barrier height of the A-state of different carbenes follows a trend of CFCl > CFBr > CFI. 11,12,17,24 The barrier height of CFCl was experimentally determined to be 4073 cm −1 , 12 which was about 1700 cm −1 smaller than the result calculated at the CASPT2(18,12)/cc- 11 For CFBr, the latest LIF spectroscopic study 17 with sub-Doppler resolution gave a barrier height of about 1000 cm −1 , more than 2300 cm −1 smaller than the result from the early LIF and photofragment excitation spectrum, 24 which was attributed to the reassigned T 00 value of the Ã1A″ state. The newest experimental T 00 value 17 of CFBr (Ã1A″) was verified by recent high-level MRCI 18,20 and CASPT2 22 calculations.…”

Geometries, vibrational frequencies, and excitation energies of a series of fluorine-substituted carbenes, FCX (X = H, F, Cl, Br, and I): A high-level multireference configuration interaction study

“…To date, most experimental studies concerned the small fluorine‐substituted carbenes, FCH, and CF 2 . Because the early emission and absorption spectroscopic studies of CF 2 were carried out several decades ago, many experimental efforts have been made to determine the structure and spectroscopic constants of the ground and first excited singlet states of FCH (and/or FCD(isotope of FCH)), CF 2, FCCl, as well as FCBr, , using a variety of laser‐based spectroscopic techniques. For some carbenes, experimental studies for the spectrum and dynamics of the states beyond the A state were carried out recently, for example, the B state of FCH and dissociation dynamics of FCCl and FCBr at 193 nm .…”

High resolution spectroscopy of the Ã1B1–A1 transition of CBr2

“…The best results are obtained when spectra with full rotational resolution are recorded, but the size of the rotational constants requires, for many carbenes, a sub-Doppler technique. We recently used a high resolution, optical parametric oscillator (OPO) laser system developed in our laboratory to obtain spectra for CFBr with full rotational resolution [4]. This led to a significant reassignment of the electronic origin of the à 1 A 00 -X 1 A 0 transition.…”

“…Two laser sources were used, including a conventional, grating tuned dye laser with a resolution of about 0.1 cm À1 and an injection seeded OPO laser system developed in Bristol with a resolution of <0.01 cm À1 . More details are provided elsewhere [4,16,17].…”

“…An interesting characteristic of this class of radicals is that their lowest-lying singlet and triplet states are close in energy which has consequences for both their reactivity and spectra and the electronic spectroscopy of carbenes, particularly halocarbenes, has been the subject of many studies [1][2][3][4][5]. The best results are obtained when spectra with full rotational resolution are recorded, but the size of the rotational constants requires, for many carbenes, a sub-Doppler technique.…”