PubMed Health⌕ Search

Biomedical subjects

V Spirko

Publications and source records attributed to V Spirko.

10 recordsLinked to original sources
PubMed2006

Theoretical study of the CS2+ dication.

The potential energy and spin-orbit coupling functions of 11 lowest electronic states of CS(2+) dication have been calculated using internally contracted multireference configuration method. Using these functions, the positions and widths of the corresponding vibronic levels have been evaluated by means of the stabilization and log-phase-amplitude methods. The states governing the second step in the sequential pathway CS2(3+)-->S++CS2+-->S++C++S+ of the overall three-body Coulomb explosion of CS(2)3+ have been determined.

Carbon Compounds, Inorganic↗
PubMed2006

Computed lifetimes of metastable states of CO2+.

Highly correlated internally contracted multireference configuration interaction wave functions are used to calculate the potential energy and spin-orbit coupling functions for the lowest electronic states of CO2+ dication. Using these functions, the positions and lifetimes of the corresponding vibronic states are evaluated by means of log-phase-amplitude, stabilization, and complex-scaling methods within the framework of a multichannel Schrodinger analysis. For the first time in the literature, the calculated lifetimes are in good agreement with the experiment, thereby proving the reliability of the predicted characteristics and adequacy of the used theory for a theoretical study of other molecular dications.

Carbon Monoxide↗
PubMed2004

Calculation of the photodetachment cross sections of the HCN- and HNC- dipole-bound anions as described by a one-electron Drude model.

The Drude model for treating the interaction of excess electrons with polar molecules is extended to calculate continuum functions and to evaluate photodetachment cross sections. The approach is applied to calculate the cross sections for photodetachment of dipole-bound electrons from HCN(-) and HNC(-). In addition, an adiabatic model separating the angular and radial degrees of freedom of the excess electron is introduced and shown to account in a qualitative manner for the cross sections.

Journal Article↗
PubMed2000

Double tunneling: An overlooked quantum effect in anionic molecular clusters

Simultaneous tunneling of an electron and nuclei in hydrogen-bonded molecular clusters which support a dipole bound electron is reported. A whole class of systems including hydrogen halide and water dimer anions is predicted to exhibit this effect. A measurable signature of double tunneling is a strong reduction of the tunneling splitting compared to the neutral cluster. Quantum mechanical calculations give for the hydrogen fluoride dimer anion a ground-state tunneling splitting of 114 MHz, while for the first excited vibrational state the tunneling splitting reaches 4.20 GHz.

Journal Article↗
PubMed2000

Rovibrational Energies of Triatomic Molecules by Means of the Rayleigh-Schrödinger Perturbation Theory.

A Rayleigh-Schrödinger perturbation theory approach based on the adiabatic (Born-Oppenheimer) separation of vibrational motions was previously developed and used to evaluate for a system of coupled oscillators the adiabatic energy levels and their nonadiabatic corrections. This method is applied here to calculate rotation-vibration energies of the triatomic molecular ions HeH(+)(2) and ArNO(+) consisting of a strongly bound diatomic fragment and a relatively loosely bound rare gas atom. In these systems the high-frequency stretching motion of the diatomic fragment can be separated from the other two low-frequency motions without substantial loss of accuracy. Treating the diatomic fragment as a rigid rotor, the low-frequency stretching motion is decoupled from the bending motion in analogy to the concept of the adiabatic (Born-Oppenheimer) separation of motions and the strong nonadiabatic couplings between these two motions are accounted for perturbationally. Although the resulting perturbation series may show poor convergence, they turn out to be accurately summable by applying standard techniques for the summation of divergent series. Comparison with the results obtained from full-dimensional calculations for the two ions shows that the approach is capable of providing accurate energies for quite a few of the bound rotation-vibration states and that in the case of the HeH(+)(2) ion it is even able to predict the positions and widths of some low-lying resonance states with good accuracy. The perturbation approach yields zeroth-order energies and corrections in terms of the relevant quantum numbers. It thus allows a direct assignment of the energy levels without any reference to the corresponding eigenfunctions. The weak couplings between the high- and low-frequency motions can easily be treated by the same perturbative approach and numerically exact energies can finally be obtained. Copyright 2000 Academic Press.

Journal Article↗
PubMed1997

Ab initio Calculated Rotation-Vibration Linestrengths for HeH2+

Together with the recently determined potential energy surface for the ground electronic state of HeH2+ [V. Spirko and W. P. Kraemer, J. Mol. Spectrosc. 172, 265-274 (1995)], the electric dipole moment components were calculated directly as expectation values with the corresponding length operators at the center of mass of the ion and using the variationally optimized configuration interaction wavefunctions. From the fitted potential energy and dipole moment functions all bound rotation-vibration energy levels and the line strengths of all dipole-allowed bound-bound transitions were evaluated variationally within the framework of the Sutcliffe-Tennyson Hamiltonian. Strong transitions, especially for the (He...H2)+ stretching motion, were obtained in the 500-800 cm-1 infrared frequency range. The present calculations demonstrate that the conditions for detecting the still unobserved rotation-vibration spectrum of HeH2+ are rather promising. Copyright 1997Academic Press

Journal Article↗