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Molecular photoionization cross sections by Stieltjes-Chebyshev moment theory applied to Lanczos pseudospectra
Ist Teil von
The Journal of chemical physics, 2009-02, Vol.130 (6), p.064104-064104-8
Ort / Verlag
United States: American Institute of Physics
Erscheinungsjahr
2009
Quelle
American Institute of Physics
Beschreibungen/Notizen
Stieltjes imaging technique is widely used for the
ab initio
computation of photoionization cross sections and decay widths. The main problem hampering the application of the standard Stieltjes imaging algorithms in conjunction with high-level
ab initio
methods to polyatomic molecules is the requirement of full diagonalization of excessively large Hamiltonian matrices. Here we show that the full diagonalization bottleneck can be overcome by applying the Stieltjes imaging procedure to Lanczos pseudospectrum of the atomic or molecular Hamiltonian. Using the helium and neon atoms as examples, we demonstrate that the Lanczos pseudospectrum obtained after only a relatively small number of iterations can be used for Stieltjes-type calculations of photoionization cross sections essentially without loss of accuracy. The new technique is applied to the calculation of the total photoionization cross section of benzene within an
ab initio
approach explicitly taking into account single and double electronic excitations. Good agreement with experimental results is obtained.