R. Düren
Max Planck Society
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Featured researches published by R. Düren.
Journal of Chemical Physics | 1993
Bernd Heumann; K. Weide; R. Düren; Reinhard Schinke
The photodissociation of H2S through excitation in the first absorption band (λ≊195 nm) is investigated by means of extensive ab initio calculations. Employing the MRD‐CI method we calculate the potential energy surfaces for the lowest two electronic states of 1A‘ symmetry varying both HS bond distances as well as the HSH bending angle. (In the C2v point group these states have electronic symmetry 1B1 and 1A2, respectively.) The lower adiabatic potential energy surface is dissociative when one H atom is pulled away whereas the upper one is binding. For the equilibrium angle of 92° in the electronic ground state they have two conical intersections, one occurring near the Franck–Condon point. Because of the very small energy separation between these two states nonadiabatic coupling induced by the kinetic energy operator in the nuclear degrees of freedom are substantial and must be incorporated in order to describe the absorption and subsequent dissociation process in a realistic way. In the present work we ...
Chemical Physics Letters | 1980
Erhard W. Rothe; U. Krause; R. Düren
Abstract Dissociating Na2 B(1Πu) molecules produce Na 2P 3 2 which then emit the resonance D2 line at 5890 A. This radiation is found to have a degree of polarization of minus 5 ± 1%. This is the first observation of polarized atomic radiation resulting from dissociation, an effect predicted in 1968 by van Brunt and Zare.
Journal of Chemical Physics | 1981
R. Düren; Wolfgang Gröger; Eckart Hasselbrink; R. Liedtke
For the systems Na(3 2P3/2)Ar, NaKr, and NaXe we have measured the total differential cross sections at thermal energies. All systems show a well resolved oscillation structure of the cross sections. For these data quantum mechanical calculations have been performed based on pseudopotentials (for NaAr), and calculations in the elastic WKB approximation using a Lennard‐Jones (8,6) potential (for NaAr, NaKr, and NaXe). The results allow us to determine the interatomic potentials with high accuracy. A comparison is made by a detailed listing of experimental and theoretical results published up to now.
Journal of Chemical Physics | 2000
Jan Weiß; J. Hauschildt; S. Yu. Grebenshchikov; R. Düren; Reinhard Schinke; Jacek Koput; S. Stamatiadis; Stavros C. Farantos
A detailed analysis of the bound-state spectrum of HOCl (hypoclorous acid) in the ground electronic state is presented. Exact quantum mechanical calculations (filter diagonalization) are performed employing an ab initio potential energy surface, which has been constructed using the multireference configuration-interaction method and a quintuple-zeta one-particle basis set. The wave functions of all bound states up to the HO+Cl dissociation threshold are visually inspected in order to assign the spectrum in a rigorous way and to elucidate how the spectrum develops with energy. The dominant features are (1) a 2:1 anharmonic resonance between the bending mode and the OCl stretching mode, which is gradually tuned in as the energy increases, and (2) a saddle-node bifurcation, i.e., the sudden birth of a new family of states. The bifurcation is further investigated in terms of the structure of the classical phase space (periodic orbits, continuation/bifurcation diagram). It is also discussed how the spectrum of...
Chemical Physics Letters | 1999
J. Hauschildt; Jan Weiß; Christian Beck; S. Yu. Grebenshchikov; R. Düren; Reinhard Schinke; Jacek Koput
Abstract The dissociation of HOCl in its electronic ground state is investigated by means of quantum dynamics calculations (filter diagonalization and harmonic inversion of the autocorrelation function) and an ab initio potential energy surface. At threshold, the state-resolved rate constants are scattered over seven orders of magnitude, which is significantly broader than the distribution predicted by random matrix theory. This remarkable state specificity is the fingerprint of the regular dynamics of HOCl even at high energies.
Journal of Chemical Physics | 1980
R. Düren; G. Moritz
The alkali–rare gas potentials are recalculated using the Baylis model for the electronic interaction. Discrepancies with experimental results found in earlier applications of this model are due mainly to numerical approximations. A more realistic cutoff function for the polarization term is introduced and its influence is investigated. For Na–Ne the model fails to reproduce the experimental results. For the A 2Π potential of Na–Ar, Kr, and Xe the remaining discrepancies, which are now entirely due to the model, are 10%–30% for the well depth and 10% for the equilibrium distance.
Chemical Physics Letters | 1990
Bernd Heumann; Klaus Kühl; K. Weide; R. Düren; Bernd A. Hess; U. Meier; Sigrid D. Peyerimhoff; Reinhard Schinke
A three-dimensional potential energy surface for the second excited state of water, B1A1, is calculated by the MRD-CI method. It is employed in classical trajectory calculations to study the photodissociation in the second absorption band. We find, in accordance with experimental data, vibrational excitation of OH(2Σ) to be generally weak. This result can be readily explained in terms of the calculated potential surface.
Chemical Physics Letters | 1991
Bernd Heumann; R. Düren; Reinhard Schinke
Abstract We present extensive MRD CI ab initio calculations for the first two excited states of 1A″ symmetry (1B1 and 1A2 in the C2v point group). Full three-dimensional potential energy surfaces are constructed by varying both HS-bond lengths as well as the HSH bending angle. The lower adiabatic potential is dissociative whereas the upper one is binding. These surfaces, together with the transition dipole moments with the ground electronic state, form the basis for future investigations of the photodissociation of hydrogen sulfide.
Chemical Physics Letters | 1976
R. Düren
Abstract A calculation of some alkali-mercury potentials based on pseudopotentials for the valence electron is described. Fitting the ground state potential for Na, K and Cs to experimental values, the lowest excited states are determined. The Na-Hg potential is described in detail, the equilibrium data for Na, K, Rb and Cs interacting with Hg are given.
Chemical Physics Letters | 1978
R. Düren; W. Gröger
Abstract The differential cross sections for the interaction of Na with Ar has been measured in an atomic beam experiment at thermal collision energies. The data yield 0.85 × 10 −14 erg for the well depth and 5.05 × 10 −8 cm for the equilibrium distance. The result is compared with experimental and calculated results given previously.