Laser-induced fluorescence from the predissociating formyl radical. Part 2. - Analysis of dispersed emission from the Ã-X̃ transition

Gary Rumbles, Edward K C Lee, James J. Valentini

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Abstract

Using laser-induced fluorescence spectroscopy dispersed emission spectra of HCO and DCO have been recorded. The formyl radical was produced by the UV photolysis of acetaldehyde (d0 and d4) and detected via the à 2A″-X̃ 2A′ transition, with excitation into single vibronic levels of the first excited state. We report, for the first time, emission into the overtone of the C - H stretching frequency, demonstrating the large anharmonic motion of this, the weakest of known CH bonds. Also, the fully resolved emission bands of DCO are shown. The three fundamental modes of DCO are observable, as a result of an accidental degeneracy of the three vibrational frequencies ω1 ≈ 2ω2 ≈ ω3. The spectra are interpreted and the associated vibrational frequencies are calculated and compared with ab initio calculations. Additional bands recorded in the absence of a photolysis laser have been attributed to Raman scattering from the parent acetaldehyde.

Original languageEnglish
Pages (from-to)3837-3841
Number of pages5
JournalJournal of the Chemical Society - Faraday Transactions
Volume86
Issue number23
DOIs
Publication statusPublished - 1990

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Acetaldehyde
Photolysis
Vibrational spectra
laser induced fluorescence
acetaldehyde
Fluorescence
photolysis
Lasers
Fluorescence spectroscopy
Excited states
Stretching
Raman scattering
excitation
emission spectra
methylidyne
Raman spectra
harmonics
spectroscopy
lasers

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Laser-induced fluorescence from the predissociating formyl radical. Part 2. - Analysis of dispersed emission from the Ã-X̃ transition. / Rumbles, Gary; Lee, Edward K C; Valentini, James J.

In: Journal of the Chemical Society - Faraday Transactions, Vol. 86, No. 23, 1990, p. 3837-3841.

Research output: Contribution to journalArticle

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N2 - Using laser-induced fluorescence spectroscopy dispersed emission spectra of HCO and DCO have been recorded. The formyl radical was produced by the UV photolysis of acetaldehyde (d0 and d4) and detected via the à 2A″-X̃ 2A′ transition, with excitation into single vibronic levels of the first excited state. We report, for the first time, emission into the overtone of the C - H stretching frequency, demonstrating the large anharmonic motion of this, the weakest of known CH bonds. Also, the fully resolved emission bands of DCO are shown. The three fundamental modes of DCO are observable, as a result of an accidental degeneracy of the three vibrational frequencies ω1 ≈ 2ω2 ≈ ω3. The spectra are interpreted and the associated vibrational frequencies are calculated and compared with ab initio calculations. Additional bands recorded in the absence of a photolysis laser have been attributed to Raman scattering from the parent acetaldehyde.

AB - Using laser-induced fluorescence spectroscopy dispersed emission spectra of HCO and DCO have been recorded. The formyl radical was produced by the UV photolysis of acetaldehyde (d0 and d4) and detected via the à 2A″-X̃ 2A′ transition, with excitation into single vibronic levels of the first excited state. We report, for the first time, emission into the overtone of the C - H stretching frequency, demonstrating the large anharmonic motion of this, the weakest of known CH bonds. Also, the fully resolved emission bands of DCO are shown. The three fundamental modes of DCO are observable, as a result of an accidental degeneracy of the three vibrational frequencies ω1 ≈ 2ω2 ≈ ω3. The spectra are interpreted and the associated vibrational frequencies are calculated and compared with ab initio calculations. Additional bands recorded in the absence of a photolysis laser have been attributed to Raman scattering from the parent acetaldehyde.

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