Santos, J. P., and F. Parente. "
Ionisation of phosphorus, arsenic, antimony, and bismuth by electron impact."
The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics 47 (2008): 339-350.
AbstractAbstract. Total ionization cross sections of neutral phosphorus, arsenic, antimony, and bismuth atoms by electron impact are reported and compared to the only available experimental results by Freund et al. [Phys. Rev. A 41, 3575 (1990)]. These calculations take into account the possibilities that some target atoms used in the experiments were in metastable states close to the ground state, the excitation-autoionization of nsnp4 excited states may be substantial, and the ions produced in experiments may be in excited, low-lying metastable states. The cross sections for direct ionization calculations are based on the BEB model by Kim and Rudd [Phys. Rev. A 50, 3954 (1994)]. Plane-wave Born cross sections scaled by the method developed by Kim [Phys. Rev. A 64, 3954 032713 (2001)] are used to determine the contributions from excitation-autoionization. The combination of the BEB model and the scaled Born cross sections is in agreement with the experimental data by Freund et al. These theoretical data are useful to experimentalists and can be used to complete data tables needed for plasma or astrophysical studies.
Morrison, J. C., S. Boyd, L. Marsano, B. Bialecki, T. Ericsson, and J. P. Santos. "
Numerical methods for solving the Hartree-Fock equations of diatomic molecules I."
Communications in Computational Physics 5 (2008): 959-985.
AbstractThe theory of domain decomposition is described and used to divide the variable domain of a diatomic molecule into separate regions which are solved independently. This approach makes it possible to use fast Krylov methods in the broad interior of the region while using explicit methods such as Gaussian elimination on the boundaries. As is demonstrated by solving a number of model problems, these methods enable one to obtain solutions of the relevant partial differential equations and eigenvalue equations accurate to six significant figures with a small amount of computational time. Since the numerical approach described in this article decomposes the variable space into separate regions where the equations are solved independently, our approach is very well-suited to parallel computing and offers the long term possibility of studying complex molecules by dividing them into smaller fragments that are calculated separately.
Palma, M. L., and J. P. Santos. "
Spin-rotation and nuclear shielding constants of sulfur hexafluoride."
Molecular Physics 106 (2008): 1241-1247.
AbstractWe present a first theoretical determination of the hyperfine coupling constants of a spherical top molecule using ab initio methods. The scalar and tensorial contributions to the spin-rotation constants and the diamagnetic and paramagnetic contributions to the nuclear shielding constant are calculated for the 32SF6 molecule. The corrections to the spin-rotation constants due to nuclear Thomas precession are evaluated and discussed. Our results are compared with previously reported experimental values.