Dipole (e,e+ion) spectroscopic studies of benzene: absolute oscillator strengths for molecular and dissociative photoionization in the VUV and soft X-ray regions

Abstract

The branching ratios for molecular and dissociative photoionization of benzene (C 6H 6) have been measured in the VUV and soft X-ray regions using dipole (e,e+ion) coincidence spectroscopy (∼1 eV FWHM) at equivalent photon energies from the first ionization threshold up to 80 eV. The absolute partial oscillator strengths (cross-sections) for molecular and dissociative photoionization have been determined by combining previously reported absolute photoabsorption oscillator strength data [J. Electron Spectrosc. Relat. Phenom. 123 (2–3) (2002) 211–223] together with the photoionization branching ratios and the (multi-dissociative-corrected) photoionization efficiency obtained from time-of-flight mass spectra reported in the present work. The fact that the photoionization efficiency has been measured as greater than unity above ∼25 eV indicates the existence of multi-dissociative products from Coulomb explosion of multiply charged ions. Appearance potentials of all ion products from benzene are also reported. The presently reported results are compared with the previously published data where possible.