V.I. Perevalov

CDSD-1000, the high-temperature carbon dioxide spectroscopic databank

Abstract We present a high-temperature version, CDSD-1000, of the carbon dioxide spectroscopic databank. The databank contains the line parameters (positions, intensities, air- and self-broadened half-widths and coefficients of temperature dependence of air-broadened half-widths) of the four most abundant isotopic species of the carbon dioxide molecule. The reference temperature is T ref =1000 K and the intensity cutoff is I cut =10 −27 cm −1 / molecule cm −2 . More than 3 million lines covering the 260–8310, 418–2454, 394–4662, and 429– 2846 cm −1 spectral ranges for 12 C 16 O 2 , 13 C 16 O 2 , 12 C 16 O 18 O , and 12 C 16 O 17 O , respectively, are included in CDSD-1000. The databank has been generated within the framework of the method of effective operators and based on the global fittings of spectroscopic parameters (parameters of the effective Hamiltonians and effective dipole moment operators) to observed data collected from the literature. Line-by-line simulations of several low- and medium-resolution high-temperature (T=800– 3000 K ) spectra have been performed in order to validate the databank. Comparisons of CDSD-1000 with other high-temperature databanks HITEMP, HITELOR, and EM2C are also given. CDSD-1000 is able to reproduce observed spectra in a more satisfactory way than the high-resolution databank HITEMP for temperatures higher than 1000 K . The databank is useful for studying high-temperature radiative properties of CO2. CDSD-1000 is freely accessible via the Internet.

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.

Effective Hamiltonian for rovibrational energies and line intensities of carbon dioxide

Abstract The reduced form of Chedin effective Hamiltonian for CO2 molecule (J. Mol. Spectrosc., 76, 430–491 (1979)) has been suggested for fitting to the spectroscopic constants Gv, Bv, Dv, and Hv of the ground electronic state. Formulas relating parameters of reduced and unreduced effective Hamiltonians have been established. The sets of parameters for both Hamiltonians are presented. They are related with a reasonable accuracy by means of established formulas. The influence of the effective Hamiltonian transformations on the parameters of the effective dipole moment operator and of its matrix elements has been studied.

Global fit of 12C16O2 vibrational–rotational line intensities using the effective operator approach

More than 5000 observed line intensities belonging to 120 vibrational bands of the 12C16O2 molecule selected from the literature have been used to fit 60 parameters of an effective dipole moment. The eigenfunctions of the effective Hamiltonian published in our recent paper have been used in the fits. The regions of ν2,3ν2,5ν2,7ν2,9ν2,and11ν2 bands have been studied. RMS deviations ranging from 2.9 to 13.3% depending on the frequency regions have been achieved. The quality of the fits and the extrapolation properties of the fitted parameters are discussed. The predictions of both line positions and line intensities for perturbed bands 21113←11102, 21113←11101, 40002←11102, 12212←02201, and 23301←02201 are given. The results are compared with the HITRAN-96 database.

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

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.

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.

T.D.S. spectroscopic databank for spherical tops: DOS version

Abstract T.D.S. is a computer package concerned with high resolution spectroscopy of spherical top molecules like CH 4 , CF 4 , SiH 4 , SiF 4 , SnH 4 , GeH 4 , SF 6 , etc. T.D.S. contains information, fundamental spectroscopic data (energies, transition moments, spectroscopic constants) recovered from comprehensive modeling and simultaneous fitting of experimental spectra, and associated software written in C. The T.D.S. goal is to provide an access to all available information on vibration-rotation molecular states and transitions including various spectroscopic processes (Stark, Raman, etc.) under extended conditions based on extrapolations of laboratory measurements using validated theoretical models. Applications for T.D.S. may include: education/training in molecular physics, quantum chemistry, laser physics; spectroscopic applications (analysis, laser spectroscopy, atmospheric optics, optical standards, spectroscopic atlases); applications to environment studies and atmospheric physics (remote sensing); data supply for specific databases; and to photochemistry (laser excitation, multiphoton processes). The reported DOS-version is designed for IBM and compatible personal computers.