Absolute photoabsorption and photoionization studies of methyl bromide using dipole electron impact and synchrotron radiation PES techniques

Absolute oscillator strengths (cross sections) have been measured for the photoabsorption of CH3Br at low resolution (1 eV fwhm) in the equivalent photon energy range from 6 to 450 eV and at high resolution (0.05 eV fwhm) from 5 to 100 eV using dipole (e,e) spectroscopy. In the valence shell and Br 3d inner shell regions of CH3Br, from the first ionization threshold to 79 eV, the photoionization efficiency, ionic photofragmentation branching ratios and absolute partial oscillator strengths for molecular and dissociative photoionization have been determined by dipole (e,e + ion) spectroscopy. The major ionic pathways of the dipole induced breakdown scheme of CH3Br have been predicted from these results and the partial photoionization oscillator strengths for production of the valence shell electronic states of CH3Br+ have been estimated. Photoelectron branching ratios for CH3Br have been measured using monochromated synchrotron radiation at photon energies from 21 to 68 eV. These have been combined with the dipole (e,e) photoabsorption data to obtain partial photoionization oscillator strengths for production of the electronic stares of CH3Br+, which have been compared with the partial oscillator strength estimates derived from the (e,e + ion) data. (C) 1997 Elsevier Science B.V.