1,721,216 research outputs found
Convergent multichannel continuum states by a general configuration interaction expansion in a B-spline basis: application to photodetachment
No full textSpline basis in variational description of discrete and continuum statesAIP Conference Proceedings
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2h-1p Cl calculations of ionization potentials of small molecules: Corrections to the koopmans theorem
No full textA Multichannel Least-Squares B-Spline Approach to Molecular Photoionization: Theory, Implementation, and Applications within the Configuration-Interaction Singles Approximation
Full text linkWe describe, in detail, a basis set approach to the multichannel scattering problem. The full set of linearly independent scattering states at each prefixed energy of the continuum spectrum can be obtained via a least-squares approach. To test the algorithm in a concrete setup, we report a parallel implementation of the close-coupling method in which the final states are treated within the configuration-interaction singles (CIS) approximation. The method requires, as input, a set of orthonormal orbitals, obtained from any quantum chemistry package. A one-center expansion (OCE) basis set consisting of products of radial B-splines and symmetry adapted angular functions is then used to expand the continuum electron wave function. To assess the quality of the CIS approximation, we compute total and partial cross sections and angular asymmetry parameters for the photoionization of a selection of closed-shell atoms (He, Ne, and Ar), H2, H2O, and ethylene. Results are compared with the experimental data and with theoretical predictions obtained with time-dependent density functional theory (TDDFT). It is seen that, generally, the photoionization observables obtained at the CIS level compare well with TDDFT predictions. The same basis can be employed to describe molecular multiphoton or strong field ionization
A CI study of the correlation effects in the (np)-1and (ns)-1photoelectron spectra of the alkali atoms
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Photoelectron Angular Distributions Beyond the Dipole Approximation. A Computational Study on the N2 Molecule
No full textContributions of the first-order nondipole terms to the photoelectron angular distributions from randomly oriented nitrogen molecules have been calculated in the framework of density functional theory and by employing a single centre expansion for the bound and continuum wavefunctions. Both valence and inner-shell ionizations have been considered in a photon energy range from threshold up to 2000 eV. Our results agree reasonably with calculations based on the random phase approximation and with the experimental data available. Our results for core ionizations confirm the most recent experimental finding of rather small nondipole effects in the near-threshold range. However, nondipole terms turn out to be quite large, even at the threshold, when individual contributions from the 1σ-1 g and 1σ-1 u ionization channels are considered. Strong interference effects leading to high-energy oscillations in the dipole and nondipole asymmetry parameters are satisfactorily explained within the Cohen-Fano model
Quasidegenerate perturbation theory configuration interaction calculations of the core and valence photoelectron spectra of Ne and Ar
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