Photoabsorption and Photoionization Cross-Sections and Asymmetry Parameters of Pyrrole in the Vacuum-Ultraviolet Energy Range.

We carried out a joint experimental and theoretical investigation of the interaction of vacuum-ultraviolet radiation with pyrrole molecules in the gas phase. A double-ion chamber spectrometer was used to measure the absolute photoabsorption cross-sections and the photoionization quantum yields from the ionization threshold to 21.5 eV using synchrotron radiation. Moreover, photoionization and neutral-decay cross-sections on an absolute scale were derived directly from the measured data. In addition, theoretical results of the photoionization cross-section (PICS) and asymmetric parameters were obtained from the ionization threshold to 50.0 eV considering all valence orbitals. These calculations were performed using the Padé approximant technique to solve the Lippmann-Schwinger equation at the static-exchange (SE) and static-exchange-polarization (SEP) levels of approximation. Comparisons are also made with the experimental and theoretical data available in the literature. We report, for the first time, experimental ionization efficiency, neutral decay cross-sections, theoretical photoionization cross-sections for each valence orbital, and several asymmetry parameters. In general, the results are consistent and in good agreement with the available data.