Dipole (e,e) spectroscopic studies of benzene: quantitative photoabsorption in the UV, VUV and soft X-ray regions

Abstract

Absolute UV and VUV photoabsorption oscillator strengths (cross sections) for the valence shell discrete and continuum regions of benzene (C 6H 6) have been measured from 4 to 56 eV using high resolution (∼0.05 eV fwhm) dipole (e,e) spectroscopy. A wide-range spectrum, spanning the UV, VUV and soft X-ray regions, from 5 to 200 eV has also been obtained at low resolution (∼1 eV fwhm), and this has been used to determine the absolute oscillator strength scale by employing valence shell TRK [i.e., S(0)] sum-rule normalization. The presently reported high and low resolution absolute photoabsorption oscillator strengths are compared with previously published data from direct photoabsorption measurements in those limited energy regions where such data are available. Evaluation of the S(−2) sum using the presently reported absolute differential photoabsorption oscillator strength data gives a static dipole polarizability for benzene in good agreement (within ∼3.4%) with published polarizability values obtained from optical measurements. Other dipole sums S( u), ( u=−1, −3, −4, −5, −6, −8, −10), and logarithmic dipole sums L( u), ( u=−1 to −6), are also determined from the presently reported absolute differential photoabsorption oscillator strength data using dipole sum-rules.