Ionic photofragmentation and photoionization of dimethyl ether in the VUV and soft X-ray regions (8.5-80 eV) - absolute oscillator strengths for molecular and dissociative photoionization

The branching ratios for molecular and dissociative photoionization of dime thyl ether (CH3OCH3, DME) have been measured in the VUV and soft X-ray regi ons using dipole (e,e+ion) coincidence spectroscopy (similar to1 eV FWHM) a t equivalent photon energies from the first ionization threshold up to 80 e V. The absolute partial oscillator strengths (cross-sections) for molecular and dissociative photoionization have been determined from recently publis hed absolute photoabsorption oscillator strength data [R. Feng, G. Cooper, C.E. Brion, Chem. Phys. 260 (2000) 391] together with the photoionization b ranching ratios and the (mufti-dissociative-corrected) photoionization effi ciency obtained from time-of-flight mass spectra reported in the present wo rk.. No stable multiply charged molecular ion(s) from DME have been found i n the present work. However, the fact that the photoionization efficiency h as been measured as greater than unity above similar to 30 eV indicates the existence of mufti-dissociative products from Coulomb explosion of multipl y charged ions. Appearance potentials of all ion products from DME are also reported. The presently reported results are compared with the previously published data where possible. (C) 2001 Elsevier Science B.V. All rights re served.