Knowledge Bank

High resolution near infrared spectra of the symmetric and anti-symmetric $CH2$ stretch of the ethyl radical, $C2H5$, is recorded and analyzed. The radical is created in a glow discharge, slit supersonic expansion. Effecient rotational cooling $(Trot14K)$ simplifies the spectra, premitting accurate determination of both ground and vibrationally excited state rotational constants. Furthermore, detailed analysis of the spectra in terms of a rigid top-rigid frame Hamiltonian yields detailed information about the ethyl potential surface, in particular, shedding light on the equilibrium geometry and the magnitude of barriers to internal $CH2-CH3$ rotation.