CH Stretch/Internal Rotor Dynamics in Ethyl Radical: High-Resolution Spectroscopy in the CD^d3-Stretch Manifold

Published

February 1, 2006

Author(s)

Thomas Haber, Andrew C. Blair, David Nesbitt

Abstract

High resolution IR absorption spectra of supersonically cooled ethyl radicals (T_rot19 K) have ben obtained in a slit supersonic jet discharge expansion, revealing first rotationally resolved data for CH stretch excitation of the methyl group. Three different vibrational bands are observed, one parallel (K=0 0) and two perpendicular (|k|=1 0), which for nearly a decoupled methyl rotor framework would correspond to summetric and (nearly degenerate) asymmetric CH stretch excitations. However, the splitting between the two asymmetric CH stretch excitations is anomalously large (125 cm^-1), signaling the presence of strong hyperconjunction between the CH^d2 radical moiety and the opposing CH bond on the methyl group. This suggests an improved zeroth order vibrational description as an isolated Ch stretch, strongly red shifted by hyperconjunction, with localized vibrations in the remaining Ch bonds split into symmetric and asymmetric stretches. Such a dynamical picture highlights a remarkably strong coupling between methyl CH stretch vibrations and C-C torsional geometry, and begins to elucidate discrepancies with previous matrix observations.

Citation

Journal of Chemical Physics

Volume

124

Pub Type

Journals

Keywords

ethyl radical, high resolution IR, hyperconjugation, slit jet expansions

Citation

Haber, T. , Blair, A. and Nesbitt, D. (2006), CH Stretch/Internal Rotor Dynamics in Ethyl Radical: High-Resolution Spectroscopy in the CD^d3-Stretch Manifold, Journal of Chemical Physics (Accessed April 25, 2024)