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

作者：Lee Shih Huang^*

来源：Journal of Chemical Physics, 2009, 131(17): 174312.

DOI：10.1063/1.3262724

• isomerisation
• molecular beams
• organic compounds
• photodissociation
• photoexcitation
• photoionisation
• spectrochemical analysis
• time of flight spectra
• translational states

After the photolysis of acetaldehyde (CH(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(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 vertical bar beta vertical bar value less than 0.05. Primary dissociations to CH(3)CO+H and CH(3)+HCO are two major paths; most CH(3)CO subsequently decomposes spontaneously to CH(3)+CO and CH(2)CO+H and most HCO decomposes to H+CO. The ternary dissociation to CH(3)+CO+H thus accounts for approximately half of the total branching. Dissociations to CH(2)CO+H(2) and CH(2)+CH(2)O are observable, but the production of CH(4)+CO is ambiguous. The productions of C(2)H(3)+OH and C(2)H(2)+H(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(1) and S(0) but a little isomerizes to ethenol followed by multichannel decomposition.

• 出版日期2009-11-7