$d_{2}$-METHOXY RADICAL DISPERSED FLUORESCENCE AND SEP SPECTROSCOPY.

Abstract

In the rotationally resolved LIF $\tilde{A} \leftarrow \tilde{X}$ spectrum of the jet-cooled $d^{2}$-methoxy radical $(CHD_{2}O)$, combination bands of $C-O (\nu_{3})$ and $C-H (\nu_{1})$ stretches $1^{1}3^{1}$ and $1^{1}3^{2}$ were assigned. Analysis of vibrationally resolved Dispersed Fluorescence (DF) and rotationally resolved Stimulated Emission Pumping (SEP) spectra recorded upon excitation of these bands reinforces LIF spectral assignments and gives C-H and C-O stretch along with pseudo-Jahn-Teller active $d_{2}$-methyl rock $(\nu^{\prime\prime}_{6},\nu^{\prime}_{6})$ vibrational frequencies in the $\tilde{X}$ state. A splitting of about ${\sim} 200 cm^{-1}$ for $1_{1}, 3_{1}1_{1}, 3_{2}1_{1}$ vibronic levels of $CHD_{2}O$ is observed and may be due to the combination of vibronic degeneracy lifting and unquenched spin-orbit interaction. The DF spectra of $CH_{3}O$ were recorded for excitation of $\tilde{X}^{2} A_{1} 3^{n} 4^{1} (n=1,2,3)$ combination bands containing asymmetric $(\nu_{4})$ stretch. $\tilde{X}^{2} E_{1} 3_{6} 4_{1}$ and $\tilde{X}^{2} E_{1} 3_{7} 4_{1}$ rovibronic levels which lie ${\sim} 500 cm^{-1}$ and $1500 cm^{-1}$, respectively, above the $\tilde{X}^{2} E CH_{3}O$ barrier for dissociation $CH_{2}O + H$ products, exhibit splitting of ${\sim} 120 cm^{-1}$.