Gas-phase photodissociation of CH{sub 3}COCN at 308 nm by time-resolved Fourier-transform infrared emission spectroscopy

Journal Article · Sat Jan 28 04:00:00 EST 2012 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.3674166· OSTI ID:22047161

Yeh, Yu-Ying; Chao, Meng-Hsuan; Tsai, Po-Yu; Chang, Yuan-Bin; Tsai, Ming-Tsang; Lin, King-Chuen ^[1]

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

By using time-resolved Fourier-transform infrared emission spectroscopy, the fragments of HCN(v= 1, 2) and CO(v= 1-3) are detected in one-photon dissociation of acetyl cyanide (CH{sub 3}COCN) at 308 nm. The S{sub 1}(A'), {sup 1}(n{sub O}, {pi}*{sub CO}) state at 308 nm has a radiative lifetime of 0.46 {+-} 0.01 {mu}s, long enough to allow for Ar collisions that induce internal conversion and enhance the fragment yields. The rate constant of Ar collision-induced internal conversion is estimated to be (1-7) x 10{sup -12} cm{sup 3} molecule{sup -1} s{sup -1}. The measurements of O{sub 2} dependence exclude the production possibility of these fragments via intersystem crossing. The high-resolution spectra of HCN and CO are analyzed to determine the ro-vibrational energy deposition of 81 {+-} 7 and 32 {+-} 3 kJ/mol, respectively. With the aid of ab initio calculations, a two-body dissociation on the energetic ground state is favored leading to HCN + CH{sub 2}CO, in which the CH{sub 2}CO moiety may further undergo secondary dissociation to release CO. The production of CO{sub 2} in the reaction with O{sub 2} confirms existence of CH{sub 2} and a secondary reaction product of CO. The HNC fragment is identified but cannot be assigned, as restricted to a poor signal-to-noise ratio. Because of insufficient excitation energy at 308 nm, the CN and CH{sub 3} fragments that dominate the dissociation products at 193 nm are not detected.

• OSTI ID: 22047161
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 4 Vol. 136; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
74 ATOMIC AND MOLECULAR PHYSICS
DISSOCIATION
EMISSION SPECTROSCOPY
FOURIER TRANSFORMATION
GROUND STATES
INFRARED SPECTRA
INTERNAL CONVERSION
ORGANIC COMPOUNDS
PHOTOLYSIS
PHOTON-MOLECULE COLLISIONS
REACTION KINETICS
SECONDARY REACTIONS
SIGNAL-TO-NOISE RATIO
VIBRATIONAL STATES