B̃ ← X̃ Vibronic Spectra and B̃-State Fluorescence Lifetimes of Methylvinoxy Isomers

Abstract

Jet-cooled laser-induced fluorescence spectra of the B̃ ← X̃ electronic transition of 1-methylvinoxy and of a cis/trans mixture of 2-methylvinoxy are presented. We observe some 50 vibronic bands in the spectrum of 1-methylvinoxy. The complexity is due to a change in the preferred methyl rotor orientation on electronic excitation. The B̃-state barrier to internal rotation is approximately 750 cm-1. The B̃-state fluorescence lifetimes decrease from about 130 ns near the origin to 26 ns for internal energy of 2700 cm-1. We observe some 22 vibronic bands in the spectrum of the cis/trans mixture of 2-methylvinoxy. The B̃-state fluorescence lifetimes decrease gradually from about 190 ns near the origin to 140 ns for internal energy of 1170 cm-1 and then very sharply at higher energy. The new spectra serve as fingerprints for identification of specific methylvinoxy isomers as products of chemical reactions of O(3P) with alkenes, as recently observed by Bersohn and co-workers.

Kinetic Study on Reactions of 1- and 2-Methylvinoxy Radicals with O2

“…11 In the kinetic experiments, the methylvinoxy radicals were detected by exciting the B-X transitions 9,11 at 340.6 nm for 1-methylvinoxy and at 340.5 nm for 2-methylvinoxy radicals. The probe light was generated by a dye laser (Lambda Physik LPD3002, p-terphenyl) pumped * Author for correspondence.…”

Theoretical spectroscopic study of acetyl (CH3CO), vinoxy (CH2CHO), and 1-methylvinoxy (CH3COCH2) radicals. Barrierless formation processes of acetone in the gas phase

“…Nevertheless, using MRCI/CASSCF/AVTZ theory, we have identified the lowest excited electronic states to assure a clean enough ground electronic state to apply the used rovibrational models. Results are shown in Table 4 and were compared with previous experimental data [22][23][24][25][26]29,31,[33][34][35][36][37][38] or data from theoretical works 39,40 .…”

“…For the CH 2 CHO isomer, the A(A")←X(A") and B(A")←X(A") transitions has been centered at 1.0 eV 26,33,34 and at 3.6 eV [22][23][24][25]33,35,36 using different experimental techniques. The B(A")←X(A") transition of CH 3 COCH 2 was found at 3.4 eV by Williams et al 37,38 who also provided internal rotation barriers. To our knowledge, all the previous experimental data concerned doublet states.…”

Slow photoelectron velocity-map imaging spectroscopy of the n-methylvinoxide anion

“…Extensive laser induced fluorescence (LIF) studies between the radicalX andB states of the n-methylvinoxy radical have been performed by Weisshaar and co-workers. 20,32 The radicals were generated from mixtures of cis-and trans-ethyl-1-propenyl ether, CH 3 CH = CHOCH 2 CH 3 , ranging in composition from 4:1 to 1:4, though the same spectrum was observed for all mixtures. Two backbone vibrations were tentatively identified in the cisB state, and considerable additional structure was attributed to hindered rotation resulting from differing orientations of the methyl group in theX andB states.…”

“…14,15 The family of vinoxy radicals also represents an important model system in electronic spectroscopy, and as such has been investigated extensively in many laboratories. 13,[16][17][18][19][20][21][22][23][24][25][26] The SEVI spectra of this series of anions are of particular interest owing to the diversity of spectral phenomena that result from moderate geometry changes upon photodetachment and the presence of different structural isomers. The SEVI spectrum of vinoxide, CH 2 CHO -, illustrated Duschinsky mixing of normal modes between the anion and the vinoxy radical and underlined the importance of including this effect in simulated spectra.…”