A5061132790- Advanced Chemical Physics Studies
- Spectroscopy and Laser Applications
- Atmospheric Ozone and Climate
- Spectroscopy and Quantum Chemical Studies
- Quantum, superfluid, helium dynamics
- Molecular Spectroscopy and Structure
- Astrophysics and Star Formation Studies
- Atomic and Molecular Physics
- Photochemistry and Electron Transfer Studies
- Cold Atom Physics and Bose-Einstein Condensates
- Mass Spectrometry Techniques and Applications
- Molecular spectroscopy and chirality
- Catalysis and Oxidation Reactions
- Photosynthetic Processes and Mechanisms
- Atomic and Subatomic Physics Research
- Molecular Junctions and Nanostructures
- Atmospheric chemistry and aerosols
- Various Chemistry Research Topics
- Inorganic Fluorides and Related Compounds
- History and advancements in chemistry
- nanoparticles nucleation surface interactions
- Hydrogen Storage and Materials
- Magnetism in coordination complexes
- Advanced NMR Techniques and Applications
- Methane Hydrates and Related Phenomena
Leiden University
2011-2024
Leiden Observatory
2003
University of Basilicata
2003
University of Connecticut
2002
CY Cergy Paris Université
2001
Centre National de la Recherche Scientifique
2001
Observatoire de Paris
2001
Instituto de Química Física Blas Cabrera
2001
Universidad de Málaga
2001
Rijksmuseum
1983-1992
Circumstellar disks are exposed to intense ultraviolet (UV) radiation from the young star. In inner disks, UV can be enhanced by more than seven orders of magnitude compared with average interstellar field, resulting in a physical and chemical structure that resembles dense photon-dominated region (PDR). This field affects chemistry, vertical disk, gas temperature, especially surface layers. The parameters which make different traditional PDRs discussed, including shape grain growth, absence...
The dissociative chemisorption of methane on metal surfaces is fundamental and practical interest, being a rate-limiting step in the steam reforming process. reaction best modeled with quantum dynamics calculations, but these are currently not guaranteed to produce accurate results because they rely potential energy based untested density functionals dynamical approximations. To help overcome limitations, here we present for first time statistically probabilities obtained ab initio molecular...
Cross sections and rate constants are presented for the rotational excitation of OH in collision with ortho para-H2, using a new ab initio interaction potential [Offer Van Hemert, J. Chem. Phys. 99, 3836 (1993)]. The cross given at number energies compared those calculated an earlier energy surface, available experimental results. A strong oscillatory behavior is found collisions ground state para-H2 which was not apparent calculations. very much reduced ortho-H2. Rate obtained by averaging...
The bound 3 2Π and repulsive 2 states of OH are strongly coupled by the action nuclear kinetic energy operator. process photodissociation absorption into is studied theoretically. adiabatic electronic eigenfunctions potential curves calculated using large configuration-interaction (CI) representations radial coupling matrix elements obtained numerical differentiation. equations for wave functions two set up in an a diabatic formulation solved integration. electric dipole transition moments...
Various ab initio methods have been employed for the study of photodissociation processes in HCl molecule. Potential curves selected singlet and triplet states dipole transition moments between calculated. The vary significantly with internuclear distance all studied. lifetime B 1Σ+ state is predicted to be 3 ns. calculations show that occurs by absorption into repulsive A 1Π bound C state, followed predissociation. theoretical cross sections oscillator strengths are good agreement...
The exchange interaction between ${^{3}\ensuremath{\Sigma}_{\mathrm{g}}}^{\ensuremath{-}}$ ${\mathrm{O}}_{2}$ molecules, as obtained from ab initio calculations for a singlet, triplet, and quintet dimer, can be well represented by the Heisenberg Hamiltonian. coupling parameter $J$ depends exponentially on ${\mathrm{O}}_{2}$-${\mathrm{O}}_{2}$ distance, with exponents ranging 3.6 to 4.2 ${\mathrm{\AA{}}}^{\ensuremath{-}1}$ different orientations. For most orientations is antiferromagnetic,...
Results of ab initio calculations for the four lowest excited states both A′ and A″ have been discussed. In multireference configuration interaction calculations, a large Rydberg basis set has used. Three-dimensional potential energy surfaces, matrix elements transition dipole moment between ground X̃ state, electronic angular momentum operator à state B̃ presented. The show that above about 124 nm photodissociation can be well described by three states, X̃, Ã, B̃. results allow realistic...
The long-timescale behavior of adsorbed carbon monoxide on the surface amorphous water ice is studied under dense cloud conditions by means off-lattice, on-the-fly, kinetic Monte Carlo simulations. It found that CO mobility strongly influenced morphology substrate. Nanopores provide strong binding sites, which can effectively immobilize adsorbates at low coverage. As coverage increases, these sites are gradually occupied leaving a number admolecules with ability to diffuse over surface....
Water is an important molecule in interstellar and circumstellar environments. Previous observations of mid-infrared rotational lines OH suggest that these may be used to probe the photodissociation water. In this work, cross sections for H$_2$O resolving state fragment are collected incorporated a new molecular excitation code called GROSBETA, which includes radiative pumping, collisional (de)excitation, prompt emission (i.e., following production excited states). We find line intensities...
A complete three-dimensional quantum mechanical description of the photodissociation water in B̃ band, starting from its rotational ground state, is presented. In order to include B̃-X̃ vibronic coupling and B̃-Ã Renner–Teller coupling, diabatic electronic states have been constructed adiabatic matrix elements angular momentum operators, following procedure developed by A. J. Dobbyn P. Knowles [Mol. Phys. 91, 1107 (1997)], using ab initio results discussed preceding paper. The dynamics...
Theoretical calculations on the photodissociation of water in first absorption band have been used to test accuracy three available potential energy surfaces for excited state water: well-known coupled electron pair approximation Staemmler and Palma [Chem. Phys. 93, 63 (1985)], two new multireference double excitation configuration interaction surfaces: Dobbyn–Knowles surface (unpublished), Leiden [R. van Harrevelt M. C. Hemert, J. Chem. 112, 5777 (2000)]. Exact quantum mechanical...
We present calculations of cross sections for fine-structure excitation in collisions carbon and silicon ions the 2P state with atomic hydrogen ground state. The results are based on accurate CH+ SiH+ molecular potentials, including electronic core correlation relativistic effects. find that energy dependence is largely determined by shape resonances. Our work improves previous less potentials. Analytical expressions cooling efficiency C+(2P1/2) Si+(2P1/2) given temperature interval 15-2000 K.
Rotational and vibrational state distributions have been measured for the OH/OD(A2Σ+) fragment produced by photodissociation of H2O/D2O at a set wavelengths in 133−119 nm range that lead to excitation B̃(1A1) state, either directly or through particular absorption features C̃1B1 ← X̃1A1 D̃1A1 Rydberg transitions. The experimental are obtained from A2Σ+−X2Π fluorescence spectra using truncated single value decomposition method (TSVD). They compared calculated complete three-dimensional...
The photodissociation processes of CH2 into CH and H have been studied using ab initio multireference configuration-interaction methods. Two-dimensional potential energy surfaces the ten lowest triplet states correlating with seven calculated as functions bond angle one C–H distance, keeping other distance fixed at equilibrium value. Transition dipole moments connecting excited ground state obtained well. It is shown that efficient (X 2Π)+H can occur by absorption from X̃ 3B1 (1 3A″) 1 3A1...
The results for the calculation of CH+ formation rate by radiative association are presented. is performed on lowest potential energy curves, which coupled spin-orbit and rotational interaction. coefficient calculated at temperatures up to 1000 K. energy-dependent marked presence many resonances, responsible significant contributions rate. lower than that predicted a previous quantum calculation. An analytical expression temperature-dependent given interval 5-1000
Transition states and reaction paths for a hydrogen molecule dissociating on small aluminum clusters have been calculated using density functional theory. The two lowest spin taken into account all the Aln considered, with n=2–6. dimer, which shows Π3u electronic ground state, has also studied at coupled cluster configuration interaction level comparison to check accuracy of single determinant calculations in this special case, where degenerate configurations should be account. barriers give...
A new line list for rovibrational and rotational transitions, including fine structure, within the NH X³Σ⁻ ground state has been created. It contains intensities in form of Einstein f-values, all possible bands up to v' = 6, J between 25 44. The are based on a dipole moment function (DMF), which calculated using internally contracted multi-reference configuration interaction method with an aug-cc-pV6Z basis set. programs RKR1, LEVEL, PGOPHER were used calculate positions most recent...
CO2 ice is one of the most abundant components in ice-coated interstellar ices besides H2O and CO, but favorable path to still unclear. Molecular dynamics calculations on ultraviolet photodissociation different kinds CO-H2O systems have been performed at 10 K order demonstrate that reaction between CO an OH molecule resulting from through first excited state a possible route form ice. However, our calculations, which take into account surface models, suggest there another product with higher...
For a series of ten electron molecules (HF, H2O, NH3, CH4) the molecular polarizability tensor and derivatives with respect to symmetry coordinates have been calculated from ab initio SCF wavefunctions using finite field method as well perturbation theory approaches. Raman intensities degrees depolarization derived results agree available experimental data. The zeroth order bond model atom dipole interaction analysed. Both models can be used describe computed static polarizabilities...
Photodesorption of CO ice is suggested to be the main process that maintains a measurable amount gaseous in cold interstellar clouds. A classical molecular dynamics simulation used gain insight into underlying mechanism. Site-site pair potentials were developed on basis ab initio calculations for ground and excited nonrigid dimer. Both amorphous crystalline clusters created characterized by their densities, expansion coefficients, binding energies, specific heats, radial distribution...