New developments in the theory of molecular K‐shell photoionization

Abstract

AbstractA new version of the relaxed core Hartree–Fock approximation with a fractional charge of the molecular ion state is applied for calculations of molecular photoionization processes. The set of continuous spectrum wave functions obtained by that method is used when taking many‐electron correlations into account in the framework of the random‐phase approximation. The vibrational motion is also included into consideration. In that way, the most reliable results for the vibrationally resolved partial photoionization cross sections and the angular asymmetry parameter β for the K‐shells of CO and N2 molecules have been obtained. A good agreement with the state‐of‐the‐art experimental data is demonstrated. From our calculations it follows that the nondipole effects for the K‐shells of N2 and CO molecules are small near the ionization thresholds, in agreement with the latest experimental data. Two predictions have been made based on these calculations. One of them is the appearance of the correlational maximum in the photoionization cross section of the 1σu shell of N2 molecule near the σ* shape resonance, which is now fully confirmed by the experiment. The second prediction concerns the behavior of the nondipole parameters for the 1σg and 1σu shells of N2. According to our calculation, they oscillate in antiphase with rather large amplitudes around the unresolved values, so that after summation of the contributions of the two K‐shells, the oscillations practically disappear. This prediction does not yet have an experimental confirmation. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007