Gaussian Type Orbitals basis sets for the calculation of continuum properties in molecules: the differential photoionization cross section of acetylene

The integral and the differential cross sections of the valence one-photon ionization of C2H2 are computed in the Random Phase Approximation using large L-2 basis sets of Gaussian Type Orbitals (GTO's) and a K-matrix based technique. The use of special Polynomial Spherical GTO's allows an adequate representation of the short range part of the orbitals lying in the electronic continuum. Ionization channels originating from the 1 pi(u), 3 sigma(g) 2 sigma(u) and 2 sigma(g) occupied orbitals are considered, both in Separated and Interacting Channel approaches. An accurate account of the effect of the interaction between the different ionization channels is found to be mandatory in order to reproduce some of the features observed in photoelectron experimental spectra, (C) 2000 Elsevier Science B.V. All rights reserved.