Vl.G. Tyuterev

The 1997 spectroscopic GEISA databank

The current version GEISA-97 of the computer-accessible database system GEISA (Gestion et Etude des Informations Spectroscopiques Atmospheriques: Management and Study of Atmospheric Spectroscopic Information) is described. This catalogue contains 1,346,266 entries. These are spectroscopic parameters required to describe adequately the individual spectral lines belonging to 42 molecules (96 isotopic species) and located between 0 and 22,656 cm-1. The featured molecules are of interest in studies of the terrestrial as well as the other planetary atmospheres, especially those of the Giant Planets. GEISA-97 contains also a catalog of absorption cross-sections of molecules such as chlorofluorocarbons which exhibit unresolvable spectra. The modifications and improvements made to the earlier edition (GEISA-92) and the data management software are described. GEISA-97 and the associated management software are accessible from the ARA/LMD (Laboratoire de Meteorologie Dynamique du CNRS, France) web site: http://ara01.polytechnique.fr/registration.

Reduced effective Hamiltonian for Coriolis-interacting νn and νt fundamentals of C3v molecules☆

Abstract Reduction of the effective Hamiltonian for Coriolis-interacting νn(A1) and νt(E) fundamentals in C3v molecules is caried out. Formulas for the parameters of the reduced Hamiltonian in terms of the parameters of the unreduced one are derived. The reduction procedure allows interperation of the disagreement between the results reported by various authors on simultaneous fitting of interacting ν2 and ν5 bands of CH3F. It is found also that the reduction of the effective Hamiltonian for the isolated degenerate band νt(E) should be carried out in order to provide a correct interpretation of the fitted parameters in terms of molecular constants.

GLOBAL FITTING OF 12C16O2 VIBRATIONAL–ROTATIONAL LINE POSITIONS USING THE EFFECTIVE HAMILTONIAN APPROACH

About 13 000 experimental lines of the principal isotopic species of CO2 selected from the literature have been used to derive about 100 parameters of a reduced effective Hamiltonian built up to sixth order in the Amat–Nielsen ordering scheme. This Hamiltonian has been obtained from an effective Hamiltonian describing all vibrational–rotational energy levels in the ground electronic state and containing in explicit form all resonance interaction terms due to the approximate relations between harmonic frequencies ω1≈2ω2andω3≈ω1+ω2. An RMS deviation of 0.001 cm-1 has been achieved in the fitting. In order to test its predictive capabilities, the model has been used to calculate the line positions of six bands: 05511←05501, 1005(1, 2)←1004(1, 2), 1006(1, 2)←1005(1, 2), and 20033←00001, which are compared with experimental lines not included in the data set. The results are discussed and compared with the predictions of the Direct Numerical Diagonalization technique.

The MIRS computer package for modeling the rovibrational spectra of polyatomic molecules

Abstract The MIRS spectroscopic software for the modeling of ro-vibrational spectra of polyatomic molecules is presented. It is designed for the global treatment of complex band systems of molecules to take full account of symmetry properties. It includes efficient algorithms based on the irreducible tensor formalism. Predictions and simultaneous data fitting (positions and intensities) are implemented as well as advanced options related to group theory algebra. Illustrative examples on CH 3 D, CH 4 , CH 3 Cl and PH 3 are reported and the present status of data available is given. It is written in C ++ for standard PC computer operating under Windows. The full package including on-line documentation and recent data is freely available at the URL: http://www.u-bourgogne.fr/LPUB/MIRS.html .

The Virtual Atomic and Molecular Data Centre (VAMDC) Consortium

The Virtual Atomic and Molecular Data Centre (VAMDC) Consortium is a worldwide consortium which federates atomic and molecular databases through an e-science infrastructure and an organisation to support this activity. About 90% of the inter-connected databases handle data that are used for the interpretation of astronomical spectra and for modelling in many fields of astrophysics. Recently the VAMDC Consortium has connected databases from the radiation damage and the plasma communities, as well as promoting the publication of data from Indian institutes. This paper describes how the VAMDC Consortium is organised for the optimal distribution of atomic and molecular data for scientific research. It is noted that the VAMDC Consortium strongly advocates that authors of research papers using data cite the original experimental and theoretical papers as well as the relevant databases.

Ambiguity of spectroscopic parameters in the case of accidental vibration—rotation resonances in tetrahedral molecules. r2J and r2J2 terms for E-F2 interacting states

Abstract The ambiguity of spectroscopic parameters in the case of accidental vibration—rotation resonances in tetrahedral molecules is discussed. Equations ar

Variational EKE-calculations of rovibrational energies of the ozone molecule from an empirical potential function

Abstract We report rovibrational calculations from an empirical potential energy surface (PES) of the electronic ground state of ozone, using an Exact Kinetic Energy (EKE) operator. The PES was optimised using the EKE Hamiltonian and experimental spectroscopic high-resolution data. The RMS deviation of calculations for all experimental band centres directly observed so far in high-resolution spectra is 0.12 cm −1 . The RMS deviation of calculations of rotational energies up to J ⩽5 is 0.002 cm −1 for the (000) level and 0.015 cm −1 for five lowest vibrational states. Both rotational and vibrational calculations are more accurate than presently available EKE-calculations for O 3 . The PES shows a physically meaningful long-range behaviour at the dissociation limit.

Parameters of reduced Hamiltonian and invariant parameters of interacting E and F2 fundamentals of tetrahedral molecules: ν2 and ν4 bands of 12CH4 and 28SiH4

Abstract The problem of unambiguous processing of experimental data for interacting doubly and triply degenerate states of tetrahedral molecules is studied on the basis of 85 fits of ν2 and ν4 spectra of 12CH4 and 28SiH4. The formalism of irreducible tensors of the paper by J. P. Champion and G. Pierre [J. Mol. Spectrosc. 79, 255–280 (1980)] is used. The behavior of correlated parameters of the Hamiltonian expansion is examined first by series of actual fits of experimental data. It is shown that any of the q2J2- or q2J3-type parameters of the ν 2 ν 4 dyad may be given positive or negative or zero values without deterioration of the quality of fits. The other parameters move along trajectories which are described by PTZ equations [V. I. Perevalov, Vl. G. Tyuterev, and B. I. Zhilinskii, Chem. Phys. Lett. 104, 455–461 (1984)] with an accuracy of better than 5% (in the case of CH4). The experimental values of PTZ coefficients are determined. The nonlinear trajectories relating the isolated state and the interacting state models are presented as well. In order to achieve unambiguous fits the properties of the reduced Hamiltonian are studied in detail considering the influence of removing various terms from the Hamiltonian on the correlation matrix and on the standard deviation of fits σ. Twenty parameters of the reduced Hamiltonian are determined which reproduce 698 energy levels of ν 2 ν 4 of CH4 up to J = 20 with the experimental accuracy = 0.003 cm−1. Invariant q2J2-type parameters are introduced, and their values are determined for ν 2 ν 4 of 12CH4 and 28SiH4. Attention is paid to the fact that the latter approach would enable one to determine an unambiguous physically meaningful set of spectroscopic parameters and simultaneously achieve the absolute minimum of σfit.

The generating function approach to the formulation of the effective rotational Hamiltonian: A simple closed form model describing strong centrifugal distortion in water-type nonrigid molecules

Abstract We deal with the problem of the divergence of the standard power series expansion of the effective rotational Hamiltonian for high rotational levels. The paper describes a very simple model (G-operator) which takes into account the dominant part of the anomalous centrifugal distortion in H 2 O-type nonrigid quasilinear molecules in a closed form. This model is derived by taking account of the most important part of the bending-rotational interaction in the zero-order approximation. The main features of the model discussed above are the following. The high-order coefficients of the Taylor series expansion of the model are in accordance with experimental centrifugal distortion parameters for H 2 O. To a realistic approximation, the new model may be considered as a generating function for Watsons expansion of the rotational Hamiltonian. The “asymptotic behavior” of the calculated energies as K a → J is in qualitative agreement with available experimental data up to K a ≤ 20, contrary to the traditional approach. Direct calculations using the G-operator give much more satisfactory E JK a K c calc than those with a truncated standard power series expansion of H rot . For the H 2 O ground state in the interval of quantum numbers J 0 K a 3 4 )J we have typical discrepancies Δ E = | E obs - E cal | ≤ 0.5 cm −1 and relative errors ( Δ E E ) ≤ 0.00008 (without fitting). The analytical formulas for convergence radii of the standard rotational Hamiltonian derived with the use of the G-operator are in accordance with numerical tests and with previous “empirical” estimates. The conclusion is made that the generating function approach is applicable for quantum number values which are above the convergence radius of the standard expansion.

Reduced Effective Hamiltonians for Degenerate Vibrational States of Methane-Type Molecules'

Abstract The ambiguity of effective Hamiltonians for the fundamental degenerate states of the methane-type molecules is studied. The transformations of these Hamiltonians to reduced forms which include only empirically determinable parameters are suggested. The set of parameters fitted by Champion and Pierre for the ν4 band of CH4 (J. Mol. Spectrosc. 79, 225–280 (1980)) is found to be related to the set of parameters of Husson and Poussigue (J. Phys. 32, 859–865 (1971)) by the unitary transformation of the effective Hamiltonian.