Photofragment excitation spectroscopy of the formyl (HCO/DCO) radical: Linewidths and predissociation rates of the Ã(A″) state

Jean Christophe Loison, Scott H. Kable, Paul L. Houston, Itamar Burak

Research output: Contribution to journalArticlepeer-review

Abstract

Photofragment excitation (PHOFEX) spectra of the jet-cooled formyl (HCO and DCO) radical have been measured by monitoring laser-induced fluorescence of the CO fragment. The following Ã(A″)←X̃(A′) vibronic transitions were measured: (ν123) ←(0,0,0) where for HCO ν2 = 6-16 with ν1, ν3 = 0; ν2 = 7-12 with ν1 = 1, ν3 = 0; ν2 = 9-12 with ν1 = 0, ν3 = 1 and for DCO ν2 = 14-18 with ν13 = 0. The PHOFEX technique provides a powerful method for discriminating against strong transitions so as to allow assignment and measurement of many weaker Franck-Condon bands. The linewidths of the diffuse transitions lie in the 16-150 cm-1 (FWHM) range; they increase strongly with K′ (the projection of the total angular momentum onto the a axis) and decrease slightly with ν′2 (the number of HCO/DCO bending quanta). The linewidths are interpreted as radiationless transition rates and yield upper Ã-state lifetimes ranging from 70 to 700 fs. These data are in excellent agreement with a dynamical model of HCO/DCO curve crossing developed by R. N. Dixon [Mol. Phys. 54, 333 (1985)].

Original languageEnglish
Pages (from-to)1796-1802
Number of pages7
JournalThe Journal of Chemical Physics
Volume94
Issue number3
DOIs
StatePublished - 1991

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