15min:

T. HÄBER, A. C. BLAIR AND D. J. NESBITT, JILA, University of Colorado, Boulder, Colorado 80309-0440.

All three CH-stretch vibrations of the methyl group in ethyl radical have been measured using high-resolution infrared spectroscopy in a slit supersonic discharge expansion source. Rotational assignment and analysis has been performed on each of these spectra providing rotational and centrifugal-distortion constants. We see one A-type band, which corresponds nominally to the symmetric stretch vibration, with a band origin at 2854.1027(3) cm^-1. Instead of a nominally degenerate vibration, the methyl asymmetric CH stretch is split into two B- and C-type bands with a separation of 124.5361 cm^-1 due to internal rotation around the C-C bond. When compared to the splitting in nitromethane, an analogous model system for hindered internal rotation, this separation is substantially larger.