Excited-State Dynamics of CH₂CHO (B̃²A‘‘)

Abstract

State-specific radiative lifetimes and electronic quenching cross sections are reported for four different vibrational modes of CH2CHO (B̃2A‘‘). Ground-state vinoxy radicals are produced by 193-nm excimer laser photolysis of CH3OCHCH2, and pumped to the B̃ state by a tunable dye laser operating between 332 and 348 nm. Fluorescence decay rates are determined in the presence of 12 collision partners: He, Ar, N2, O2, CO, H2, HCl, N2O, CO2, C2H4, CH3OCHCH2, and SF6. The measured electronic quenching cross sections vary from 0.01 to 66.5 Å2. Zero pressure radiative lifetimes are found to vary from 98 ± 10 to 154 ± 18 ns, depending on the vibrational mode. Possible mechanisms for lifetime shortening and collisional quenching are discussed.

Photodissociating methyl vinyl ether to calibrate O+ethylene product branching and to test propensity rules for product channel electronic accessibility

“…Despite the fact that methyl vinyl ether has been used as a photolytic precursor of the vinoxy radical [17][18][19] for use in dynamics and spectroscopic studies, information on the branching to primary product channels or the electronic states of the photoproducts are unavailable. Work in progress by Su and Bersohn 20 has also recently sought to determine the vibrational distribution of ground-state vinoxy product from methyl vinyl ether photodissociation at 193 nm.…”

Fast beam photodissociation spectroscopy and dynamics of the vinoxy radical

“…The results presented here show that the dissociation dynamics of CH 2 CHO, the smallest alkenoxy radical, are quite different from those of the smallest alkanoxy and alkynoxy radicals, CH 3 O 10 and HCCO. 11 The vinoxy radical has been the subject of several spectroscopic [12][13][14][15][16][17][18][19] and electronic structure [20][21][22][23][24] investigations. The first spectroscopic detection of CH 2 CHO, discrete bands with a probable origin at 28 780 cm Ϫ1 , was reported by Ramsay 12 in 1965.…”

“…Previous attempts to observe photodissociation products in the gas phase using LIF have been unsuccessful. 17,18 Our experiment directly detects the presence of photodissociation, and identifies and characterizes the photodissociation products. We can therefore readily determine if dissociation occurs following excitation of the B state and learn about the detailed mechanism.…”

Laser-induced fluorescence of the CH2CFO radical

“…Spectroscopic and kinetics studies of vinoxy radicals have been carried out by a variety of methods, including UV absorption, 2 IR absorption, 2 laser-induced fluorescence, [3][4][5][6][7] microwave, 8 submillimeter-wave, 9 and ab initio theoretical calculations. [10][11][12][13] From these studies, the following characteristics of vinoxy radicals have been suggested.…”