Nonadiabatic dynamics in the photodissociation of ICH2CN at 266 and 304 nm studied by the velocity map imaging

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Photodissociation dynamics of iodoacetonitrile (ICH2CN) have been investigated at pump wavelengths of 266 and 304 nm using a photofragment ion image velocity mapping technique. At both wavelengths, the prompt C-I bond rupture takes place on the repulsive excited states to give I(P-2(3/2)) and I-*(P-2(1/2)), and their speed and spatial distributions are simultaneously measured. The recoil anisotropy parameter (beta) at 266 nm is determined to be 1.10 and 1.60 for I and I-*, respectively, while it is found to be much higher at 304 nm to give beta=1.70 and 1.90 for I and I-*, respectively. The branching ratios for I-*/I channels are measured to be 0.724 and 0.136 at 266 and 304 nm, respectively, giving insights on nonadiabatic transition phenomena and relative oscillator strengths of optically accessible transitions of ICH2CN. Accordingly, relative oscillator strengths of parallel/perpendicular transitions and nonadiabatic transitions among the excited states are quantitatively characterized. A large portion of the available energy (41%-48%) goes into the internal energy of the CH2CN fragment. A modified impulsive model in which the CH2CN fragment is assumed to be rigid predicts the energy disposal quite well. Delocalization of an unpaired electron of the CH2CN radical during the C-I bond cleavage, leading to a large structural change of the CH2CN moiety, may be responsible for internally hot fragments. (c) 2006 American Institute of Physics.
Publisher
AMER INST PHYSICS
Issue Date
2006-03
Language
English
Article Type
Article
Keywords

ENHANCED MULTIPHOTON IONIZATION; TRIATOMIC PHOTOFRAGMENT SPECTRA; METHYL-IODIDE; ALKYL IODIDES; MOLECULAR-OXYGEN; ATOMIC IODINE; UMBRELLA MODE; CH3I; BAND; PHOTOELECTRON

Citation

JOURNAL OF CHEMICAL PHYSICS, v.124, no.12, pp.65 - 70

ISSN
0021-9606
DOI
10.1063/1.2167748
URI
http://hdl.handle.net/10203/14349
Appears in Collection
CH-Journal Papers(저널논문)
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