Publikace ÚTF

The nonlocal resonance models for nuclear dynamics of low-energy electron-molecule collisions are usually constructed by fitting necessary quantities to the potential energy curves (surfaces) and the eigenphase sums obtained from fixed-nuclei quantum chemistry and scattering calculations. Moreover, the fitting functions have to be chosen in such a way to be able to evaluate the Hilbert transform, which appears in the nonlocal potential, in a closed form. This procedure can be rather elaborate for polyatomic molecules when more than one degree of freedom for nuclear motion is considered. In this paper we propose an alternative, fitting-free way of constructing these models directly from the fixed-nuclei level-shift function that is completely determined by the choice of the discrete state defining the nonlocal resonance model. The Hilbert transform is evaluated numerically using the fast Fourier transform. Using the numerically solvable two-dimensional model of resonant electron-molecule collisions, we demonstrate that the results of nonlocal models constructed using the proposed approach agree with the exact ones up to contributions from background scattering, which can often be neglected for inelastic processes. For completeness, we also compare the results of the proposed method with the usual fitting approach, showing that the proposed fitting-free method of construction of the nonlocal resonance models is more reliable and accurate.