Knowledge Bank

Resonance Reman spectroscopy has been applied to the study of the gas phase methyl radical. Resonance enhancement allows selective examination of a minority species present in low concentration with minimum interference from other species. This technique has been used to elucidate the ground state vibrational structure of $CH3$ and $CD3$. The information gained is complementary to infrared work in that the transitions that are observed are not infrared active. The results of this work compare will with literature values and theoretical predictions. Vibrational progression of, $\nu 2$, have been observed. These new observations yield the anharmonic constants for $CH3$ and $CD3$. $CD3CD3X11=-22.7\pm 1.5cm-1-9.1\pm 1.3cm-1X12=-9.8\pm 1.5cm-1-4.3\pm 1.4cm-1$ In the resonance Raman spectrum, the pattern of relative intensities of the rotational lines is a sensitive function of laser excitation frequency and excited state linewidth. By fitting the resonance Reman spectrum the excited state lifetime can be $determined.1$ An examination of the vibrational structure of observed absorption bands is also in progress.