LASER EXCITATION AND DISPERSED FLUORESCENCE SPECTRA OF METHOXY PRODUCED BY PHOTODISSOCIATION IN A PULSED SUPERSONIC JET EXPANSION

Author Institution: Department of Chemistry, Florida State University; Laser Spectroscopy Facility. Department of Chemistry, The Ohio State UniversityMethoxy is a highly reactive organic free radical that is a key intermediate in the combustion of hydrocarbon fuels and in atmospheric reactions. It has nominal C3y symmetry and an electronically degenerate 2E ground state and is therefore subject to Jahn-Teller distortion and also split by a moderately large ($-60 cm^{-1}$) spin-orbit coupling. The origin of the electronic transition $\bar{A} ^{2} A_{1} \longleftrightarrow \bar{X} ^{2}E$ of methoxy in the ultraviolet has been reported in the literature to have several different values over the years. Extensive laser-induced fluorescence excitation spectra and wavelength resolved emission spectra have been recorded at low temperatures for methoxy, $CH_{3}O$, and its perdeutero analog, $CD_{3}O$. A detailed analysis of the vibronic spectrum of methoxy has yielded a new reliable value for the electronic origin and an essentially complete set of significantly revised vibrational frequencies for both the $\bar{X}$ and $\bar{A}$ states. These results have been used to determine the vibronic structure of the ground state and in the elucidation of several ambiguous excited state vibronic assignments