Electronic absorption spectrum of CH₃O

Abstract

The Ã2A1-X̃2E electronic transition of CH3O, which is qualitatively analogous to the Ã2Σ+-X̃2Πi transition of OH, has been detected in absorption. It consists of a long series of vibronic bands described by v=(31538±9)+v′3(676±5)- v′32(5.7±0.6 cm-1), where v is the transition wavenumber at the band intensity maxima, and v3 is the upper state C-O stretching vibrational quantum number. The estimated oscillator strength of the transition, f=(4±2)×10-4, has the same magnitude as in OH. It is shown that the observed C-O vibrational frequencies and vibronic intensities are consistent with the ab initio SCF geometry of CH3O, and with Franck-Condon factors derived from it. Earlier difficulties in detecting the absorption spectrum are attributed to a low absorption coefficient, and to the marginal thermodynamic stability of the CH3O ground state. © 1979 American Institute of Physics.