Dynamics of multidissociation paths of acetaldehyde photoexcited at 157 nm: Branching ratios, distributions of kinetic energy, and angular anisotropies of products

Journal Article · Sat Nov 07 04:00:00 EST 2009 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.3262724· OSTI ID:21559802

Lee, Shih-Huang ^[1]

---

1. National Synchrotron Radiation Research Center (NSRRC), 101 Hsin-Ann Road, Hsinchu Science Park, Hsinchu 30076, Taiwan (China)

After the photolysis of acetaldehyde (CH{sub 3}CHO) at 157.6 nm in a molecular-beam apparatus using photofragment translational spectroscopy and vacuum-ultraviolet photoionization to detect products, we observed 13 photofragments associated with six primary dissociation channels and secondary dissociation of products CH{sub 3}CO and HCO. We measured time-of-flight spectra and spatial angular anisotropies of products and evaluated the branching ratios of products. All photoproducts have nearly isotropic angular distributions with an average |{beta}| value less than 0.05. Primary dissociations to CH{sub 3}CO+H and CH{sub 3}+HCO are two major paths; most CH{sub 3}CO subsequently decomposes spontaneously to CH{sub 3}+CO and CH{sub 2}CO+H and most HCO decomposes to H+CO. The ternary dissociation to CH{sub 3}+CO+H thus accounts for approximately half of the total branching. Dissociations to CH{sub 2}CO+H{sub 2} and CH{sub 2}+CH{sub 2}O are observable, but the production of CH{sub 4}+CO is ambiguous. The productions of C{sub 2}H{sub 3}+OH and C{sub 2}H{sub 2}+H{sub 2}O indicate that isomerization from acetaldehyde to ethenol occurs before fragmentation. After photoexcitation to the n-3p state, most acetaldehyde converts into states T{sub 1} and S{sub 0} but a little isomerizes to ethenol followed by multichannel decomposition.

• OSTI ID: 21559802
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 17 Vol. 131; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ACETALDEHYDE
ALDEHYDES
ALKANES
ALKYL RADICALS
ANGULAR DISTRIBUTION
ANISOTROPY
BEAMS
BRANCHING RATIO
CHEMICAL REACTIONS
DECOMPOSITION
DIMENSIONLESS NUMBERS
DISSOCIATION
DISTRIBUTION
ENERGY
FORMALDEHYDE
HYDROCARBONS
IONIZATION
ISOMERIZATION
ISOMERS
KINETIC ENERGY
METHANE
MOLECULAR BEAMS
ORGANIC COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOIONIZATION
PHOTOLYSIS
RADICALS
SPECTRA
SPECTROSCOPY
TIME-OF-FLIGHT METHOD
VINYL RADICALS