DIRECT MEASUREMENT OF THE TRANSITION DIPOLE-MOMENT OF THE V(3) ASYMMETRIC C-H STRETCHING VIBRATION OF THE CH3 RADICAL

A direct measurement of the transition dipole moment, mu(3), Of the degenerate v 3 in-plane asymmetric C-H stretching vibration of the methyl radical has been made. The measurements were carried out in a flow reactor using laser-photolysis transient infrared absorption spectroscopy. Cyano (CN) radicals (and Cl atoms) were produced by laser photolysis of BrCN (or ClCN) at 193 nm and reacted with methane to give both CH3 and HCN (and HCl). The intensities of 18 rotational lines of the v(3) fundamental band were measured relative to the R(8) line of the C-H stretching vibration (v(3)) of HCN(001<--0). The best estimate of the transition dipole moment of the CH3 (001(1)0<--0) transition was provided b) the measured line intensity for the CH3 (001(1)0<--0)(r)R(3,3) transition and was determined-to be mu(3)=0.0327+/-0.0021 D. (C) 1995 American Institute of Physics.