Share Email Print
cover

Proceedings Paper

Fast-beam studies of free-radical photodissociation: the CH2NO2 radical
Author(s): David J. Leahy; Douglas R. Cyr; David L. Osborn; Daniel M. Neumark
Format Member Price Non-Member Price
PDF $14.40 $18.00
cover GOOD NEWS! Your organization subscribes to the SPIE Digital Library. You may be able to download this paper for free. Check Access

Paper Abstract

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.

Paper Details

Date Published: 22 April 1993
PDF: 12 pages
Proc. SPIE 1858, Laser Techniques for State-Selected and State-to-State Chemistry, (22 April 1993); doi: 10.1117/12.143115
Show Author Affiliations
David J. Leahy, Univ. of California/Berkeley and Lawrence Berkeley Lab. (United States)
Douglas R. Cyr, Univ. of California/Berkeley and Lawrence Berkeley Lab. (United States)
David L. Osborn, Univ. of California/Berkeley and Lawrence Berkeley Lab. (United States)
Daniel M. Neumark, Univ. of California/Berkeley and Lawrence Berkeley Lab. (United States)


Published in SPIE Proceedings Vol. 1858:
Laser Techniques for State-Selected and State-to-State Chemistry
Cheuk Yiu Ng, Editor(s)

© SPIE. Terms of Use
Back to Top