Rotational constants and centrifugal distortion constants of a molecule are the essence of its rotational or rovibrational spectrum (e.g., from microwave, millimeter wave, and infrared experiments). These parameters condense the spectroscopic characteristics of a molecule and, thus, are a valuable resource in terms of presenting and communicating spectroscopic observations. While spectroscopic parameters are obtained from experimental spectra by fitting an effective rovibrational Hamiltonian to transition frequencies, the ab initio calculation of these parameters is usually done within vibrational perturbation theory. In the present work, we investigate an approach related to the experimental fitting procedure, but relying solely on ab initio data obtained from variational calculations, i.e., we perform a nonlinear least squares fit of Watson’s A- and S-reduced rotation–vibration Hamiltonian to rovibrational state energies (resp. transition frequencies) from rotational–vibrational configuration interaction calculations. We include up to sextic centrifugal distortion constants. By relying on an educated guess of spectroscopic parameters from vibrational configuration interaction and vibrational perturbation theory, the fitting procedure is very efficient. We observe excellent agreement with experimentally derived parameters.
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21 October 2022
Research Article|
October 21 2022
Determination of spectroscopic constants from rovibrational configuration interaction calculations
Dennis F. Dinu
;
Dennis F. Dinu
(Data curation, Formal analysis, Investigation, Software, Visualization, Writing – original draft, Writing – review & editing)
1
Department of General, Inorganic and Theoretical Chemistry, University of Innsbruck
, Innrain 80/82, 6020 Innsbruck, Austria
2
Institute for Theoretical Chemistry, University of Stuttgart
, Pfaffenwaldring 55, 70569 Stuttgart, Germany
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Martin Tschöpe
;
Martin Tschöpe
(Investigation, Software, Validation, Writing – review & editing)
2
Institute for Theoretical Chemistry, University of Stuttgart
, Pfaffenwaldring 55, 70569 Stuttgart, Germany
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Benjamin Schröder
;
Benjamin Schröder
(Conceptualization, Methodology, Software, Supervision, Writing – original draft, Writing – review & editing)
2
Institute for Theoretical Chemistry, University of Stuttgart
, Pfaffenwaldring 55, 70569 Stuttgart, Germany
3
Institute of Physical Chemistry, University of Goettingen
, Tammannstr. 6, 37077 Göttingen, Germany
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Klaus R. Liedl
;
Klaus R. Liedl
(Resources, Supervision)
1
Department of General, Inorganic and Theoretical Chemistry, University of Innsbruck
, Innrain 80/82, 6020 Innsbruck, Austria
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Guntram Rauhut
Guntram Rauhut
a)
(Funding acquisition, Project administration, Resources, Supervision, Writing – original draft, Writing – review & editing)
2
Institute for Theoretical Chemistry, University of Stuttgart
, Pfaffenwaldring 55, 70569 Stuttgart, Germany
a)Author to whom correspondence should be addressed: rauhut@theochem.uni-stuttgart.de
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a)Author to whom correspondence should be addressed: rauhut@theochem.uni-stuttgart.de
J. Chem. Phys. 157, 154107 (2022)
Article history
Received:
July 28 2022
Accepted:
September 22 2022
Citation
Dennis F. Dinu, Martin Tschöpe, Benjamin Schröder, Klaus R. Liedl, Guntram Rauhut; Determination of spectroscopic constants from rovibrational configuration interaction calculations. J. Chem. Phys. 21 October 2022; 157 (15): 154107. https://doi.org/10.1063/5.0116018
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