J. Vojtík

Atoms-in-molecules calculations on diatomic fragments of polyatomic systems. HeH and HeH+

Abstract Two different modifications of the atoms-in-molecules method are applied to various states of the HeH and HeH + species. The calculations are carried out in a wide range of internuclear separations in order to obtain a description of the diatomics adequate to serve as input for a subsequent DIM calculation of potential energy surfaces of (HeH 2 ) + . The results are compared with other presently available calculations.Abstract Two different modifications of the atoms-in-molecules method are applied to various states of the HeH and HeH + species. The calculations are carried out in a wide range of internuclear separations in order to obtain a description of the diatomics adequate to serve as input for a subsequent DIM calculation of potential energy surfaces of (HeH 2 ) + . The results are compared with other presently available calculations.

Ab initio calculation of deuteron quadrupole coupling constants for low-lying rovibrational levels of HD in its X 1Σg+ and B 1Σu+ states

Abstract Deuteron quadrupole coupling constants of rovibrational levels of HD in its X 1 Σ g + B 1 Σ u + states have been calculated from molecular wavefunctions which explicitly describe vibrational motion. The quadrupole coupling constants obtained exhibit significant vibrational and rotational dependence. A marked difference between the X 1 Σ g + and B 1 Σ u + is predicted. Some aspects for the future theoretical interpretation of the hyperfine structure of laser-induced fluorescence and infrared saturated absorption spectra of diatomic molecules are outlined.

Hermitean DIM model for potential energy surfaces relevant to chemiionization processes

Abstract A new version of the diatomics-in-molecules (DIM) approach to the calculation of basic characteristic of chemiionization processes is presented. In this scheme the description of a resonant state (including the prediction of its width) is based on the diagonalization of only one hermitean matrix. A sample calculation on the He(2 3 S)H 2 system is reported.

A semi-empirical dim calculation of the resonant energy and autoionization width of the He(23S)—H2 system

Abstract The DIM method is used to compute the resonant energy and the autoionization width for a wide range of configurations of the He(2 3 S)—H 2 syste

Diatomics-in-molecules calculation of the potential energy surfaces relevant to penning ionization in the He(2 3S)H2 system

Potential energy surfaces and the autoionization width for the Penning ionization transition He(2 3S) + H2 → He + H+2 + e− have been calculated using the DIM method. The surfaces compare favourably with the existing ab initio calculations, and the approximation to the autoioinization width appear to be reasonable.

Diatomics-in-molecules correlation diagrams for (BH2)+

Abstract The diatomics-in-molecules method is applied to calculate potential energy surfaces of the system B + ( 1 S, 3 P) + H 2 (X 1 Σ g + . Results are presented as correlation diagrams following the approximate minimum energy paths for C ∞v and C 2v geometries of the reactants. Two possible non-adiabatic mechanisms of complex formation are discussed.

Atoms-in-molecules calculations on diatomic fragments of polyatomic systems. FH and FH+

Abstract Two versions of the atoms-in-molecules method (the original Moffitt scheme and the orthogonalized Moffitt method) are applied to various states of the FH and FH − species to obtain information on diatomic state mixing and potential energy curves needed for a diatomic-in-molecules calculation on (FH 2 ) + .

Ab initio calculation of nuclear quadrupole coupling constants of rovibrational levels in the X 1Σ+ state of all isotopic variants of BH

Abstract The 11 B, 10 B, and 2 H quadrupole coupling constants of rovibrational levels of 11 B 2 H, 10 B 2 H, 11 B 1 H, and 10 B 1 H in their ground electronic state have been calculated from molecular wavefunctions which explicitly describe nuclear displacement. The 11 B and 10 B coupling is predicted to be relatively very strong for all isotopic variants. The vibrational dependence of the B coupling is found to be rather insignificant and its rotational dependence is predicted to be quite unimportant. The deuteron coupling in 10 B 2 H and 11 B 2 H is found to be weak, its strength is predicted to decrease with vibrational excitation. The change with rotational excitation is unimportant. The quadrupole hyperfine patterns of 10 B 2 H and 11 B 2 H in the X 1 Σ + state are dominated by relatively very strong B coupling and their basic features are predicted to be independent of the vibrational and rotational state considered.

Surface crossing in interaction of atomic hydrogen with a lithium metal cluster

Abstract Interaction of atomic hydrogen with a (4,1,4) lithium cluster, simulating the (100) metal surface, is studied using the diatomics-in-molecules method. Ground-and excited-state potential curves for normal approach ofH to some attack positions on the surface intersect or pseudo-intersect. The results reveal possible non-adiabatic character of the absorption process.

Break-down of the born-oppenheimer approximation in the He(23S)-H2 and He(21S)-H2 autoionizing systems?

Abstract The possibility of non-adiabatic behaviour of the He(21S)-H2 and He(23S)-H2 collision systems is reexamined by means of extended diatomics-in-molecules calculations. In the triplet case, the calculations support the idea that at collision energies above ≈ 1 eV the system could behave non-adiabatically. In the singlet He*-H2 system, a break-down of the Born-Oppenheimer approximation is predicted to take place at higher energies.