Józef E. Sienkiewicz

Theoretical study of highly-excited states of KRb molecule

Semi-empirical adiabatic potential energy curves of highly excited states of the KRb molecule are calculated as a function of the internuclear distance R over a wide range from 3 to 150 a0. The diatomic molecule is treated as an effective two-electron system by using the large core pseudopotentials and core polarization potentials. All calculations are performed by using the nonrelativistic CASSCF/MRCI method with accurate basis set functions. The spectroscopic constants of the calculated electronic states agree well with experimental data, including the recent ones from Lee et al., and with available theoretical results.

Critical minima in elastic scattering of electrons from Ar and Zn

Abstract Ab initio relativistic calculations have been carried out to search for critical minima in the angle and energy differential cross-sections for the elastic scattering of electrons from argon and zinc atoms. Theoretical approach is based on the Dirac–Hartree–Fock method. Exchange between incident and target electrons is calculated exactly. Target polarization is described by an ab initio potential taken from relativistic polarized orbital calculations. Comparison is made with experimental data and other theoretical results.

Possible schemes of photoassociation processes in the KLi molecule with newly calculated potential energy curves

We present four promising schemes for photoassociative formation of KLi molecule in its ground electronic state. Analysis is based on newly calculated adiabatic potentials supported by transition dipole moments and Franck-Condon factors.

Potential energy surfaces of the low-lying electronic states of the Li + LiCs system

Abstract Ab initio quantum chemistry calculations are performed for the mixed alkali triatomic system. Global minima of the ground and first excited doublet states of the trimer are found and Born-Oppenheimer potential energy surfaces of the Li atom interacting with the LiCs molecule were calculated for these states. The lithium atom is placed at various distances and bond angles from the lithium-caesium dimer. Three-body nonadditive forces of the Li 2 Cs molecule in the global minimum are investigated. Dimer-atom interactions are found to be strongly attractive and may be important in the experiments, particularly involving cold alkali polar dimers.

Theoretical treatment of charge transfer processes: From ion/atom to ion/biomolecule interactions

A unified approach is proposed for the treatment of charge transfer processes occurring in collisions of ions on atomic or molecular targets. The theoretical treatment, including ab initio molecular calculations of the potential energy curves and couplings followed by a semi-classical collision dynamics, is extended in particular to polyatomic molecules of biological interest. The method is presented on the example of the important astrophysical reaction S 3+ (3s 2 3p) + H, and extended to the charge transfer of the RNA base Uracil onto C q+ ions (q = 2-5). In that sense a simple model is proposed, correlated to experimental investigations on ionization and fragmentation processes in C q+ -Uracil collisions.

Relativistic multiconfiguration method in low-energy scattering of electrons from argon atoms

For the first time the differential cross sections of the elastic scattering of slow electrons from argon atoms are calculated in a relativistic multiconfiguration method. The correlation effects responsible for target polarization are treated in a relativistic configuration–interaction scheme that allows for dynamical effects. Calculations of the differential cross sections and spin polarization are discussed and compared with experimental and other theoretical data.

Electronic structure and rovibrational predissociation of the 21Π state in KLi

Adiabatic potential energy curves of the 31Σ+, 33Σ+, 21Π and 23Π states correlating for large internuclear distance with the K(4s) + Li(2p) atomic asymptote were calculated. Very good agreement between the calculated and the experimental curve of the 21Π state allowed for a reliable description of the dissociation process through a small (∼20 cm-1 for J = 0) potential energy barrier. The barrier supports several rovibrational quasi-bound states and explicit time evolution of these states via the time-dependent nuclear Schrödinger equation, showed that the state populations decay exponentially in time. We were able to precisely describe the time-dependent dissociation process of several rovibrational levels and found that our calculated spectrum match very well with the assigned experimental spectrum. Moreover, our approach is able to predict the positions of previously unassigned lines, particularly in the case of their low intensity.

Adiabatic potential energy surfaces of the vinoxy radical

The three adiabatic potential surfaces of the vinoxy radical are calculated. They describe the ground and two lowest excited states. We employ the MCSCF (CASSCF) method using the MOLPRO package.

Adiabatic potentials of the N 5+ +He and Si 4+ +He pairs for the charge transfer studies

Adiabatic potential-energy curves of the low-lying 1Σ+, 3Σ+, 1Π and 3Π states have been determined for the N5++He and Si4++He systems. An ab initio calculation method with configuration interaction by means of the MOLPRO numerical code have been employed.