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Now showing items 1-10 of 76

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Aufsatz
Computation of relativistic symmetry orbitals for finite double point groups

(1989)

A program is presented for the construction of relativistic symmetry-adapted molecular basis functions. It is applicable to
36 finite double point groups. The algorithm, based on the projection operator method, automatically generates linearly
independent basis sets. Time reversal invariance is included in the program, leading to additional selection rules in the
non-relativistic limit.

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Aufsatz
On the total energy of two-electron atoms

(1985)

Using the Multi-Configuration Dirac-Fock (MCDF) method we calculate with 9 configuration state functions the correlation energy as well as the total energy of the lowest J = 0 ground state of all two-electron systems from H- to Thorium (Z = 90). A comparison with experimental data, which are available only in the low Z region, shows a very good agreement.

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Aufsatz
Relativistic Dirac-Fock-Slater program to calculate potential-energy curves for diatomic molecules

(1986)

A LCAO-MO (linear combination of atomic orbitals - molecular orbitals) relativistic Dirac-Fock-Slater program is presented, which allows one to calculate accurate total energies for diatomic molecules.
Numerical atomic Dirac-Fock-Slater wave functions are used as basis functions. All integrations as well as the solution of the Poisson equation are done fully numerical, with a relative accuracy of 10{^-5} - 10{^-6}. The details of the method as well as first results are presented here.

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

(1987)

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.

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Aufsatz
Theoretical evidence for quasi-molecular structure at small internuclear distances in elastic ion-atom scattering

(1985)

The potential energy curve of the system Ne-Ne is calculated for small internuclear
distances from 0.005 to 3.0 au using a newly developed relativistic molecular Dirac-Fock-Slater code. A significant structure in the potential energy curve is found which
leads to a nearly complete agreement with experimental differential elastic scattering cross sections. This demonstrates the presence of quasi-molecular effects in elastic ion-atom collisions at keV energies.

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Aufsatz
Evidence for an additional coupling of the innermost shells in very heavy quasi-molecular ion-atom collisions

(1982)

Due to the tremendous spin-orbit splitting of quasi-molecular levels in superheavy
collision systems (Z = Z_1 + Z_2 {\ge\approx} 137) bombarding energy 0.5-6 MeV N{^-1}, unusual couplings may occur around Z \simeq 165. Experimental evidence for such a theoretically predicted coupling is discussed.

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Aufsatz
Kr - Kr correlation diagram and its use in heavy-ion collisions

(1981)

A realistic self-consistent charge correlation diagram calculation of the Kr{^2+} - Kr{^2+} system has been performed. We get excellent agreement for the 4(3/2)_u level with an experimentally observed MO level at large distances. Possible reasons for discrepancies
between experiment and theory at small distances are discussed.

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

(1989)

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.

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

(1980)

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 ...

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Aufsatz
Quadrupole moments of radium isotopes from the 7p^2P_3/2 hyperfine structure in Ra II

(1989)

The hyperfine structure and isotope shift of ^{221- 226}Ra and ^{212, 214}Ra have been measured in the ionic (Ra 11) transition 7s^2 S_{1/2} - 7p ^2 P_{3/2} (\lamda = 381.4 nm). The method of on-line collinear fast-beam laser spectroscopy has been applied using frequency-doubling of cw dye laser radiation in an external ring cavity. The magnetic hyperfine fields are compared with semi-empirical and ab initio calculations. The analysis of the quadrupole splitting
by the same method yields the following, improved ...