Jet-Cooled Laser-Induced Fluorescence Spectroscopy of Some Alkoxy Radicals

Abstract

The laser-induced fluorescence spectra of jet-cooled alkoxy radicals were recorded. Spectra were observed for both isomers of propoxy and all three isomers of butoxy. In nearly all cases, the vibrational structure of the spectra are dominated by a C-O stretch progression, which, however, terminates much more abruptly for the primary isomers than for the more branched ones. For each of the radicals (except t-butoxy), a number of low-frequency (below the C-O stretch) vibrational modes were assigned by analogies among the alkoxy spectra and reference to frequencies from ab initio calculations. A few higher frequency modes were also assigned using similar approaches.

Radiative and non-radiative decay of selected vibronic levels of the B state of alkoxy radicals

“…We have previously reported [5][6][7] the laser excitation spectra of the e B B-e X X transition of all the alkoxy radicals, except ethoxy, for which lifetime measurements were attempted. The jet-cooled LIF excitation spectrum of ethoxy has been reported by several groups [8][9][10] and selected vibrational bands in this spectrum were chosen to obtain the natural lifetimes.…”

Theoretical prediction of spectroscopic constants of 1-alkoxy radicals

“…Chemical interest certainly extends to the larger alkoxy radicals, but spectroscopic data has been largely lacking. Recently several studies [13][14][15] have been reported involving LIF spectra of a non-radiative decay of the B state and dispersed fluoresence experiments 18 on the B − X emission.…”

Photoelectron spectroscopy of the hydroxymethoxide anion, H2C(OH)O−

“…[1][2][3][4][5][6][7] Many experimental and theoretical studies have focused on the effects of adding various substituents onto the methoxy radical, the simplest alkoxy radical, looking for trends in tropospheric reaction kinetics, unimolecular processes, and overall reactivity. [1][2][3][4][5]8 The hydroxymethoxy radical (H 2 C(OH)O • ) is an oxygenated alkoxy radical, proposed to be formed from the UV photofragmentation of hydroxymethyl hydroperoxide (H 2 C(OH)OOH), a product from the tropospheric oxidation of alkenes.…”

“…[1][2][3][4][5][6][7] Many experimental and theoretical studies have focused on the effects of adding various substituents onto the methoxy radical, the simplest alkoxy radical, looking for trends in tropospheric reaction kinetics, unimolecular processes, and overall reactivity. [1][2][3][4][5]8 The hydroxymethoxy radical (H 2 C(OH)O • ) is an oxygenated alkoxy radical, proposed to be formed from the UV photofragmentation of hydroxymethyl hydroperoxide (H 2 C(OH)OOH), a product from the tropospheric oxidation of alkenes. [9][10][11][12][13] In addition to the potential atmospheric importance of the H 2 C(OH)O • radical, its corresponding anion, hydroxymethoxide (H 2 C(OH)O -), is the conjugate base of methanediol (H 2 C(OH) 2 ), considered to be a molecule of astrochemical and possible prebiotic relevance [14][15][16][17][18] as a building block of simple amino acids.…”