Laser-induced fluorescence of the CH2CFO radical

Abstract

Articles you may be interested inThe electronic spectrum of the fluoroborane free radical. II. Analysis of laser-induced fluorescence and single vibronic level emission spectraThe laser-induced fluorescence spectrum, Renner-Teller effect, and molecular quantum beats in the à 2 Π i -X̃ 2 Π i transition of the jet-cooled HCCSe free radical A new laser-induced fluorescence spectrum has been observed in the region of 307-335 nm. Since this spectrum is observed when reacting oxygen atoms with CH 2 CHF, or CH 2 CF 2 , or CH 2 CFCl and also by photolysis of CH 3 CFO, the fluorescing molecule is the CH 2 CFO ͑fluoroformyl methyl͒ radical. From an analysis of the laser-induced single vibronic level fluorescence, some of the vibrational frequencies can be assigned for the ground electronic state 3 ϭ1724 cm Ϫ1 ͑C-O stretch͒, 5 ϭ1211 cm Ϫ1 ͑C-F stretch͒, 6 ϭ906 cm Ϫ1 ͑CH 2 rock͒, 7 ϭ847 cm Ϫ1 ͑C-C stretch͒, 8 ϭ584 cm Ϫ1 ͑FCO bend͒, and 9 ϭ416 cm Ϫ1 ͑CCO bend͒, for the excited state 3 ϭ1790, 5 ϭ 1253, 6 ϭ911, 7 ϭ874, 8 ϭ537, and 9 ϭ421 cm Ϫ1 . Ab initio calculations on the CH 2 CFO radical give a planar geometry with vibrational frequencies that are consistent with the observed fundamental frequencies. The vibrational frequencies show that the structure of the ground state is closer to fluoroformyl methyl ͑•CH 2 CFO) rather than a vinoxy-type (CH 2 vCFO•͒ radical. The collision-free radiative lifetimes of the excited state are 49-81 ns depending on excitation energy and vibrational modes. Strong predissociation is observed above vЈϭ1, especially in the 3 Ј mode.

Photodissociation spectroscopy and dynamics of the CH2CFO radical

“…1,6 In that work, peaks in the LIF excitation spectrum were identified based on dispersed fluorescence spectra acquired from excitation of the major bands of the B state. The wavelengths of the features observed in the PFY spectrum are in close agreement with those present in the LIF spectrum ͓see Figs.…”

“…3 Several recent experimental and theoretical studies [1][2][3] have focused on the B 2 AЉ←X 2 AЉ transition, for which T 0 ϭ29 867 cm Ϫ1 ͑3.70 eV͒. 2 Furubayashi et al 1 reported a vibrationally-resolved laser-induced fluorescence ͑LIF͒ excitation spectrum of CH 2 CFO over the range of 29 870-32 570 cm Ϫ1 . The origin band of this transition was partially rotationally resolved by Wright and Dagdigian.…”

“…3 Spectral assignments, aided by measured dispersed fluorescence spectra, revealed excitation of the 3 ͑C-O stretch͒, 4 ͑CHH scissor͒, 5 ͑C-F stretch͒, 6 (CH 2 rock͒, 7 ͑C-C stretch͒, 8 ͑FCO bend͒, and 9 ͑CCO bend͒ modes of the B state. 1,6 The LIF study by Furubayashi et The heats of formation used to obtain the heats of reaction for channels ͑1͒-͑3͒, ͑5͒, and ͑6͒ are listed in Table I, while the heat of reaction for channel ͑4͒ is obtained from the theoretical work by Cao et al 7 The energy level diagram for CH 2 CFO and these product channels is presented in Fig. 1.…”

“…Vibrationally resolved structure of the B 2 AЉ←X 2 AЉ transition is observed in the photofragment yield spectrum, extending ϳ6000 cm Ϫ1 further to the blue than the previous LIF spectrum. 1 In addition, the photodissociation dynamics have been examined with a newly implemented coincidence imaging detection scheme. 32 The photofragment mass ratios obtained illustrate that the CH 2 FϩCO and HCCOϩHF channels are present, while the F-loss channel, which is analogous to the H-loss channel observed in vinoxy, is absent.…”

The near ultraviolet spectrum of the FCO radical: Re-assignment of transitions and predissociation of the electronically excited state

“…Photolysis of CF 2 HCl in the presence of O atoms resulted only in LIF spectra of hot bands of CF 2 . 13 Recently reported LIF features, 14 assigned to FCO but differing in appearance from the UV absorption spectra in the same wavelength region, have since been shown to originate from the CH 2 CFO radical, [21][22][23][24] which was formed as a contaminant in the preparation process. The failure to observe FCO via LIF is most probably because of rapid predissociation of the electronically excited states.…”