MULTIPLET-SPECIFIC MULTICHANNEL ELECTRON-CORRELATION EFFECTS IN THE PHOTOIONIZATION OF NO

摘要

We present partial photoionization cross sections and photoelectron asymmetry parameters for the photoionization of NO leading to the (2 pi)(-1)X (1) Sigma(+), (5 sigma)(-1)b (3) Pi, (5 sigma)(-1)A (1) Pi, (4 sigma)(-1)c (3) Pi, and (4 sigma)B--1 (1) Pi states of NO+. The results were obtained with multichannel multiplet-specific interaction potentials derived from correlated target states. The resulting scattering equations were solved using the Schwinger variational method. The calculations considered excitation energies in the 10-40 eV range. It was found that selective orthogonalization eliminated spurious resonances that were encountered. We found that in the channel leading to the (2 pi)(-1)X (1) Sigma(+) state of NO+, the structure seen experimentally in the 14-17 eV region is due to two pronounced valence autoionizing states, one of which is broadened by interaction with a shape resonance. We predict the existence of a third strong sigma --> pi(*) transition of (2) Sigma(-) symmetry in the photoabsorption cross section at approximately 14.8 eV photon energy which, due to symmetry restrictions, cannot decay by autoionization. In addition, our results indicate that the broad structure seen experimentally in the 20-40 eV region in the (2 pi)(-1) channel might be due to coupling to shape resonances which occur in other ionization channels. Our predicted total cross sections and photoelectron asymmetry parameters differ from those obtained by previous theoretical approaches, all of which neglected correlation effects. The present results were found to be in good agreement with the available experimental data. We found that the existence and position of the various resonances were sensitive to the level of correlation and interchannel coupling included in the calculation. In particular, we (5 sigma)(-1)A (1) Pi states of NO+ was due to a single 5 sigma --> sigma(*) resonant state which decayed into both ionization channels. (C) 1996 American Institute of Physics. [References: 34]