An attempt on the calculation of relativistic potential energy curves: noble gas difluorides

Total energy SCF calculations were performed for noble gas difluorides in a relativistic procedure and compared with analogous non-relativistic calculations. The discrete variational method with numerical basis functions was used. Rather smooth potential energy curves could be obtained. The theoretical Kr - F and Xe - F bond distances were calculated to be 3.5 a.u. and 3.6 a.u. which should be compared with the experimental values of 3.54 a.u. and 3.7 a.u. Although the dissociation energies are off by a factor of about five it was found that ArF_2 may be a stable molecule. Theoretical ionization energies for the outer levels reproduce the experimental values for KrF_2 and XeF_2 to within 2 eV.

A clear atomic example for the surface sensitivity of penning ionization

Using a crossed-beam apparatus with a double hemispherical electron spectrometer, we have studied the spectrum of electrons released in thermal energy ionizing collisions of metastable He^*(2^3S) atoms with ground state Yb(4f^14 6s^2 ^1S_0) atoms, thereby providing the first Penning electron spectrum of an atomic target with-4f-electrons. In contrast to the HeI (58.4nm) and NeI (73.6/74.4nm) photoelectron spectra of Yb, which show mainly 4f- and 6s-electron emission in about a 5:1 ratio, the He^*(2^3S) Penning electron spectrum is dominated by 6s-ionization, acoompnnied by some correlation- induced 6p-emission (8% Yb+( 4f^14 6p^2P) formation) and very little 4f-ionization (<_~ 2.5%). This astounding result is attributed to the electron exchange mechanism for He^*(2^3S) ionization and reflects the poor overlap of the target 4f-electron wavefunction with the 1s-hole of He^*(2^3S), as discussed on thc basis of Dirac-Fock wave functions for the Yb orbitals and through calculations of the partial ionization cross sections involving semiempirical complex potentiale. The presented case may be regarded as the elearest atomic example for the surface sensitivity of He^*(2^3S) Penning ionization observed so far.

The continuation of the periodic table up to Z = 172.

The chemical elements up to Z = 172 are calculated with a relativistic Hartree-Fock-Slater program taking into account the effect of the extended nucleus. Predictions of the binding energies, the X-ray spectra and the number of electrons inside the nuclei are given for the inner electron shells. The predicted chemical behaviour will be discussed for a11 elements between Z = 104-120 and compared with previous known extrapolations. For the elements Z = 121-172 predictions of their chemistry and a proposal for the continuation of the Periodic Table are given. The eighth chemical period ends with Z = 164 located below Mercury. The ninth period starts with an alkaline and alkaline earth metal and ends immediately similarly to the second and third period with a noble gas at Z = 172. Mit einem relativistischen Hartree-Fock-Slater Rechenprogramm werden die chemischen Elemente bis zur Ordnungszahl 172 berechnet, wobei der Einfluß des ausgedehnten Kernes berücksichtigt wurde. Für die innersten Elektronenschalen werden Voraussagen über deren Bindungsenergie, das Röntgenspektrum und die Zahl der Elektronen im Kern gemacht. Die voraussichtliche Chemie der Elemente zwischen Z = 104 und 120 wird diskutiert und mit bereits vorhandenen Extrapolationen verglichen. Für die Elemente Z = 121-172 wird eine Voraussage über das chemische Verhalten gegeben, sowie ein Vorschlag für die Fortsetzung des Periodensystems gemacht. Die achte chemische Periode endet mit dem Element 164 im Periodensystem unter Quecksilber gelegen. Die neunte Periode beginnt mit einem Alkali- und Erdalkalimetall und endet sofort wieder wie in der zweiten und dritten Periode mit einem Edelgas bei Z = 172.

{2p_\pi}-{2p_\sigma} crossing in heavy symmetric ion-atom collisions: I. Level structure

Ab initio self-consistent DFS calculations are performed for five different symmetric atomic systems from Ar-Ar to Pb-Pb. The level structure for the {2p_\pi}-{2p_\sigma} crossing as function of the united atomic charge Z_u is studied and interpreted. Manybody effects, spin-orbit splitting, direct relativistic effects as well as indirect relativistic effects are differently important for different Z_u. For the I-I system a comparison with other calculations is given.

Influence of the electronic shell structure on the elastic scattering of heavy ions

The interatomic potential of the system I - I at intermediate and small distances is calculated from atomic DFS electron densities within a statistical model. Structures in the potential, due to the electronic shells, are investigated. Calculations of the elastic differential scattering cross section for small angles and several keV impact energies show a detailed peak pattern which can be correlated to individual electronic shell interaction.

Electronic structure calculations of small AI_n (n = 2 - 8) clusters

The electronic states of small AI_n (n = 2 - 8) clusters have been calculated with a relativistic ab-initio MOLCAO Dirac-Fock-Slater method using numerical atomic DFS wave-functions. The excitation energies were obtained from a ground state calculation of neutral clusters, and in addition from negative clusters charged by half an electron in order to account for part of the relaxation. These energies are compared with experimental photoelectron spectra.

Interpretation of quasimolecular L X-rays in heavy-ion collisions

Using a relativistic selfconsistent correlation diagram a first interpretation of the shape and position of L MO X-rays is given within a quasi-adiabatic model.

Interpretation of noncharacteristic M X-rays in heavy colliding systems by selfconsistent relativistic molecular calculations

The result of the first calculation of a self-consistent relativistic many electron correlation diagram ever done (for the system Au - I) leads to a good agreement of the spectral shape and position of the observed noncharacteristic X-rays within the quasi adiabatic model.

An ab-initio calculation of the Coulomb explosion of N_2 after heavy-ion bombardement

Self-consistent-field calculations for the total potential energy of highly ionized N_2 molecules are presented. We compare these calculations to the experimentally observed energy released in the Coulomb explosion of ionized N_2 molecules created after collision with fast heavy ions. The most important electronic states of the fragment ions are determined.

Many-electron relativistic calculation and interpretation of atomic processes in time dependent heavy-ion scattering

The time dependence of a heavy-ion-atom collision system is solved via a set of coupled channel equations using energy eigenvalues and matrix elements from a self-consistent field relativistic molecular many-electron Dirac-Fock-Slater calculation. Within this independent particle model we give a full many-particle interpretation by performing a small number of single-particle calculations. First results for the P(b) curves for the Ne K-hole excitation for the systems F{^8+} - Ne and F{^6+} - Ne as examples are discussed.

Relativistic many-electron SCF correlation diagram for superheavy quasimolecules: Pb - Pb

We present the first relativistic many-electron SCF correlation diagram for a superheavy quasimolecule: Pb - Pb. The discussion shows a large number of quantitative as well as qualitative differences as compared with the known one-electron correlation diagram.

Total differential scattering cross section of {Ar^+}-Ar at 15 to 400 keV

We report on the measurement of the total differential scattering cross section of {Ar^+}-Ar at laboratory energies between 15 and 400 keV. Using an ab initio relativistic molecular program which calculates the interatomic potential energy curve with high accuracy, we are able to reproduce the detailed structure found in the experiment.