Ksenia Sosnova

Dual-kinetic-balance approach to the Dirac equation for axially symmetric systems: Application to static and time-dependent fields

Dual kinetic balance (DKB) technique was previously developed to eliminate spurious states in the finite-basis-set-based solution of the Dirac equation in central fields. In the present paper, it is extended to the Dirac equation for systems with axial symmetry. The efficiency of the method is demonstrated by the calculation of the energy spectra of hydrogenlike ions in presence of static uniform electric or magnetic fields. In addition, the DKB basis set is implemented to solve the time-dependent Dirac equation making use of the split-operator technique. The excitation and ionization probabilities for the hydrogenlike argon and tin ions exposed to laser pulses are evaluated.

Exterior complex scaling method in TDDFT: HHG of Ar atoms in intense laser fields

The exterior complex scaling (ECS) method is applied in the framework of time-dependent density-functional theory (TDDFT) to study high-order harmonic generation (HHG) of multielectron atoms in intense laser fields. With the help of ECS, correct outgoing-wave boundary conditions can be imposed on the wave functions at large distances. In our implementation, ECS is combined with the time-dependent generalized pseudospectral method for accurate and efficient solution of the time-dependent Kohn-Sham equations. We make use of LB94 exchange-correlation potential which appears quite accurate in calculations of unperturbed electronic structure of Ar. Calculations of HHG are performed for the laser fields with the wavelength of 800 nm and several peak intensities. The HHG spectrum exhibits an intensity-independent minimum corresponding to the photon energy of about 51 eV which is closely related to the Cooper minimum in the photoionization cross section of Ar. We found that HHG spectra calculated with the frozen-core potential (not including dynamic response of the electron density) differ significantly from those obtained by TDDFT.

Dual Kinetic Balance Approach to Basis-Set Expansions for axially symmetric Dirac equation

The study of the interaction of highly charged ions with laser fields requires solving the time-dependent Dirac equation. The Dual Kinetic Balance (DKB) technique enables one to eliminate the spurious states occurring in the numerical solutions of the Dirac equation obtained with finite basis set methods. Initially developed for the radial Dirac equation, here the DKB method is generalized to the three-dimensional systems with the axial symmetry. Efficiency of the method is demonstrated by calculating the spectra of hydrogenlike ions and the ionization probability of a H-like ion by a laser pulse.