G. Raşeev

Partial photoionization cross section and photoelectron angular distribution for the X 2Σg+ state of N2+ in the static‐exchange approximation

The partial photoionization cross section of N2 leading to the production of N2+ in its X 2Σg+ ground state is calculated in the single‐center frozen core static‐exchange approximation. The initial and final states are antisymmetrized products using SCF molecular orbitals of either N2 or N2+ ground states. All these calculations reproduce well the σu shape resonance in the partial cross section. The photoelectron angular distribution is also calculated and the average over the vibrational motion is performed. The R‐averaged results are in agreement with recent measurements using synchrotron radiation. The branching ratio of the cross sections leading N2+ in its two lowest vibrational states compares rather well with the experimental values obtained recently by West et al.

Ab initio approach to the multichannel quantum defect calculation of the electronic autoionisation in the Hopfield series of N2

The two-step formulation of the multichannel quantum defect theory, applied to molecular electronic autoionistion by Giusti-Suzor (1980) and Lefebvre-Brion (1973) is used to calculate the total and partial photoionisation cross sections in the region of the Hopfield series on N2, the 700-730 AA wavelength range. The electronic quantities necessary for this treatment are obtained from ab initio calculations. The cross sections and the photoelectron angular distribution parameters are in satisfying agreement with experiment. The results clearly show that the absorption series correspond to the (B2 Sigma u+)nd sigma g series and the apparent emission series to the (B2 Sigma u+)nd pi g series.

Unimolecular reaction paths of electronically excited species. IV. The C̃ 2Σ+g state of CO+2

The geometrical structure of the low‐lying states of CO+2 has been calculated ab initio. The C 2Σ+g/2A1 state is found to be slightly bent in its equilibrium geometry. A new assignment of the vibrational structure of the corresponding band in the photoelectron spectrum is suggested. State C is predissociated by two competitive channels. One of them leads to O++CO, the other to CO++O. The mechanism of these predissociations involves a slow, rate‐determining, intersystem crossing to a bent a 4B1 state. The population of state a has a choice between dissociating to O++CO fragments and undergoing a further, much faster, intersystem crossing to the ground state X which dissociates to CO++O. Since radiationless transitions between X and a are relatively rapid, the state which is lower in energy (i.e., X) has a much larger population than the other (i.e., a). Hence, the CO++O channel prevails as soon as it is energetically accessible. The rate‐determining step of both processes is the intersystem crossi...

Theoretical study of shape resonances in the partial photoionization cross sections for the b 4Σg− and B 2Σg− states of O2+

Using the single‐center static‐exchange approximation, the 3σg photoionization cross section of O2 is calculated. The R‐averaged results are obtained for the production of O+2 in the b 4Σ−g and B 2Σ−g states. Shape resonances, a few electron volts wide, are found at 3 and 2.5 eV from the threshold for these two states, respectively. We find reasonable agreement with the experimental cross sections for the B 2Σ−g state and with the β values for the b 4Σ−g state. For this last state, comparison between theory and experiment leads us to a possible interpretation of the data, but a definite answer can not be given without taking into account the autoionized Rydberg states.

Lifetime of excited electronic states at surfaces: CO−(2π*) resonance on Cu(111) and Cu(100) surfaces

A model study of the (2π*) resonance in the CO/Cu(1 1 1) and CO/Cu(1 0 0) systems is presented. Although the CO−(2π*) resonance is located inside the surface projected band gap in both systems, it is found to be very short-lived. These results are at variance with the apparently similar alkali/Cu systems where a strong reduction of the resonance decay by one-electron transfer to the substrate as compared to a free-electron metal surface is observed and attributed to the presence of the surface projected band gap. The differences between the two systems are analysed, allowing a discussion of the situations where a projected band gap induced stabilisation can be expected. The present results are compared with recent experimental results obtained by time resolved 2-photon photo emission.

Theoretical approach to the Cooper minimum in hydrogen iodide

Abstract Calculations of the photoionization cross section corresponding to the X 2 Π (5pπ) −1 ion state and of the angular asymmetry parameter β are performed for the HI molecule in the 10.4–92 eV range. Within the frozen-core static exchange approximation, no Cooper minimum is found in the cross section, contrary to experiment. Interchannel coupling with the continuum states corresponding to ion states associated with a 4d hole is also partially taken into account. Two energy points are calculated within this coupling scheme, showing better agreement with experiment, especially for β at high energies.

Adsorption sites and migration of a carbon monoxide molecule on stepped vicinal surfaces of Cu(211) and Cu(511)

Motivated by recent scanning tunneling microscopy (STM) and helium-atom scattering experiments, the adsorption of a carbon monoxide molecule on Cu(211) and Cu(511) stepped vicinal surfaces is studied by analyzing the interaction potential and performing classical dynamics simulations both in the canonical and microcanonical ensembles. For both (211) and (511) surfaces we found two adsorption sites, nearly equivalent energetically, located nearly on top above the border-row atoms of a terrace. These sites, favored by a large available phase space, have the highest adsorption probability in agreement with STM results on the CO/Cu(211) system. At low temperatures hindered translation of CO is anisotropic along the different crystallographic directions. For both surfaces, the migration is favored along rows but there are significant differences between Cu(211) and Cu(511).

An efficient method for the transformation of two electron integrals

A n5 order algorithm for the transformation of two electron integrals is described. This algorithm minimizes both multiplications and input output operations.