Communication: Photodissociation of CH{sub 3}CHO at 308 nm: Observation of H-roaming, CH{sub 3}-roaming, and transition state pathways together along the ground state surface

Journal Article · Wed Jan 28 04:00:00 EST 2015 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.4906457· OSTI ID:22416031

Li, Hou-Kuan; Tsai, Po-Yu; Hung, Kai-Chan; Kasai, Toshio; Lin, King-Chuen ^[1]

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1. Department of Chemistry, National Taiwan University, Taipei 106, Taiwan and Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan (China)

Following photodissociation of acetaldehyde (CH{sub 3}CHO) at 308 nm, the CO(v = 1–4) fragment is acquired using time-resolved Fourier-transform infrared emission spectroscopy. The CO(v = 1) rotational distribution shows a bimodal feature; the low- and high-J components result from H-roaming around CH{sub 3}CO core and CH{sub 3}-roaming around CHO radical, respectively, in consistency with a recent assignment by Kable and co-workers (Lee et al., Chem. Sci. 5, 4633 (2014)). The H-roaming pathway disappears at the CO(v ≥ 2) states, because of insufficient available energy following bond-breaking of H + CH{sub 3}CO. By analyzing the CH{sub 4} emission spectrum, we obtained a bimodal vibrational distribution; the low-energy component is ascribed to the transition state (TS) pathway, consistent with prediction by quasiclassical trajectory calculations, while the high-energy component results from H- and CH{sub 3}-roamings. A branching fraction of H-roaming/CH{sub 3}-roaming/TS contribution is evaluated to be (8% ± 3%)/(68% ± 10%)/(25% ± 5%), in which the TS pathway was observed for the first time. The three pathways proceed concomitantly along the electronic ground state surface.

• OSTI ID: 22416031
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 4 Vol. 142; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ACETALDEHYDE
BRANCHING RATIO
CARBON MONOXIDE
DISSOCIATION
EMISSION SPECTRA
EMISSION SPECTROSCOPY
FOURIER TRANSFORMATION
GROUND STATES
METHANE
PHOTOLYSIS
RADICALS
SURFACES
TIME RESOLUTION