22 April 1993 Fast-beam studies of free-radical photodissociation: the CH2NO2 radical
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Proceedings Volume 1858, Laser Techniques for State-Selected and State-to-State Chemistry; (1993) https://doi.org/10.1117/12.143115
Event: OE/LASE'93: Optics, Electro-Optics, and Laser Applications in Scienceand Engineering, 1993, Los Angeles, CA, United States
We report a study of the photodissociation of the nitromethyl radical utilizing a fast beam photofragment translational spectrometer. A fast radical beam is prepared via the synthesis, acceleration and subsequent photodetachment of mass-selected, internally cold nitromethyl anions. Following ultraviolet photodissociation, the recoiling photofragments are detected in coincidence by a microchannel plate detector with a time- and position-sensitive wedge-and- strip anode. The data reveal that the electronically excited nitromethyl radicals dissociate into two mass channels: (I) CH2NO2$DAG yields CH2NO + O, and (II) CH2NO2$DAG yields CH2O + NO. The branching ratio of the two channels is nearly constant at 1:1 over the excitation wavelength range of 240 - 270 nm. The kinetic energy release (KER) of channel (I) peaks at 5 - 8 kcal/mol, suggesting that the N-O bond rupture does not occur directly, as it would on a purely repulsive potential surface. The observed KER for channel (II) peaks at 52 kcal/mol, with an average of over 100 kcal/mol going into internal degrees of freedom in the fragments. This channel requires a significant rearrangement of the nuclei and has a large exit barrier. The photofragment angular distributions for both channels show little anisotropy. The absence of the channel corresponding to C-N bond rupture provides evidence that the accessed excited state(s) of nitromethyl have C-N double bond character. These observations provide qualitative information about the mechanisms for O atom loss and for rearrangement and subsequent NO elimination.
© (1993) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
David J. Leahy, David J. Leahy, Douglas R. Cyr, Douglas R. Cyr, David L. Osborn, David L. Osborn, Daniel M. Neumark, Daniel M. Neumark, "Fast-beam studies of free-radical photodissociation: the CH2NO2 radical", Proc. SPIE 1858, Laser Techniques for State-Selected and State-to-State Chemistry, (22 April 1993); doi: 10.1117/12.143115; https://doi.org/10.1117/12.143115


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