FLUORESCENCE-DIP INFRARED SPECTROSCOPY OF METHOXY RADICAL

Abstract

The fluorescence-dip infrared (FDIR) spectrum of methoxy radical (CH$_3$O) has been recorded in the region 2875-2980 cm$^{-1}$. Methoxy radical was produced by the photolysis of methyl nitrite (CH$_3$ONO) in a pulsed free-jet expansion. The laser induced fluorescence (LIF) spectrum obtained was characterized by a rotational temperature of ${\sim}$2K. In the FDIR experiment, the UV excitation laser was tuned to the rotational transition, N$^{\prime}$=1, K$^{\prime}$=0 $\leftarrow$ J$^{\prime\prime}$=3/2, P$^{\prime\prime}$=3/2 of the $\widetilde{\textit{A}}$ $^2$A$_1$ $\leftarrow$ $\widetilde{\textit{X}}$ $^2$E$_{3/2}$, 0-0 band. Two IR sources were used to deplete the ground-state level: difference frequency mixing and an optical parameter oscillator (OPO). The FDIR spectrum is detected as dips in fluorescence as a function of IR frequency. The correlation between the FDIR spectrum, the IR absorption spectrum,} \underline{\textbf{117}}, 6538, (2002)} the stimulated emission pumping (SEP) spectrum and the dispersed fluorescence (DF) spectrum will be discussed.