Empirical normal intensity distribution for overtone vibrational spectra of triatomic molecules

Medvedev, Emile S.; Ushakov, V. G.; Conway, Eamon; Upadhyay, Apoorva; Gordon, Iouli E.; Tennyson, Jonathan

doi:10.1016/j.jqsrt.2020.107084

Cited by 8 publications

(16 citation statements)

References 48 publications

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“…This value is large due to the large discrepancy between our ab initio data points and V up from POKAZATEL rather than from our fitting of V low . The 250 parameters used here are close to the 241 parameters taken by Bubukina et al (2011) and Mizus et al (2018), as well as the 245 parameters by Partridge and Schwenke (1997). The maximum values of i, j and k that we consider are 10, 8 and 15, respectively.…”

Section: Fitting the Ab Initio Surfacementioning

confidence: 60%

“…The non-adiabatic correction is an important contribution to any high-accuracy potential (Partridge and Schwenke, 1997; Schwenke, 2001;Bubukina et al, 2011;Mizus et al, 2018;Polyansky et al, 2013). For high-temperature spectra, transitions involving high values of the total angular momentum, J , become significantly more prominent and, as the non-adiabatic correction grows approximately as J 2 (Bunker and Moss, 1980), non-adiabatic effects are more important.…”

Section: Fitting the Ab Initio Surfacementioning

confidence: 99%

“…Semi-empirical adjustments which start from a highquality ab initio PES allow energy levels to be calculated to within a fraction of a wavenumber when compared to experimental measurements (Bubukina et al, 2011;Mizus et al, 2018;Partridge and Schwenke, 1997;Polyansky et al, 2018). The POKAZATEL PES (note that the POKAZATEL PES and POKAZATEL line list are distinct entities) extends to dissociation and predicts energy levels with J = 0, 2 and 5 with a root-mean-square error (RMSE) of 0.118 cm −1 .…”

Section: Introductionmentioning

confidence: 99%

“…The PES's accuracy rapidly diminishes as J grows (Polyansky et al, 2018). This rotational effect is not uncommon in semi-empirical potentials (Bubukina et al, 2011;Mizus et al, 2018;Partridge and Schwenke, 1997). The distribution of rotational energy levels makes this po-tential problematic for the generation of high-temperature spectra where transitions between high J states are important.…”

Section: Introductionmentioning

confidence: 99%

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A semi-empirical potential energy surface and line list for H216O extending into the near-ultraviolet

et al. 2020

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Abstract. Accurate reference spectroscopic information for the water molecule from the microwave to the near-ultraviolet is of paramount importance in atmospheric research. A semi-empirical potential energy surface for the ground electronic state of H216O has been created by refining almost 4000 experimentally determined energy levels. These states extend into regions with large values of rotational and vibrational excitation. For all states considered in our refinement procedure, which extend to 37 000 cm−1 and J=20 (total angular momentum), the average root-mean-square deviation is approximately 0.05 cm−1. This potential energy surface offers significant improvements when compared to recent models by accurately predicting states possessing high values of J. This feature will offer significant improvements in calculated line positions for high-temperature spectra where transitions between high J states become more prominent. Combining this potential with the latest dipole moment surface for water vapour, a line list has been calculated which extends reliably to 37 000 cm−1. Obtaining reliable results in the ultraviolet is of special importance as it is a challenging spectral region for the water molecule both experimentally and theoretically. Comparisons are made against several experimental sources of cross sections in the near-ultraviolet and discrepancies are observed. In the near-ultraviolet our calculations are in agreement with recent atmospheric retrievals and the upper limit obtained using broadband spectroscopy by Wilson et al. (2016, p. 194), but they do not support recent suggestions of very strong absorption in this region.

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Section: Fitting the Ab Initio Surfacementioning

confidence: 60%

Section: Fitting the Ab Initio Surfacementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A semi-empirical potential energy surface and line list for H216O extending into the near-ultraviolet

et al. 2020

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“…To speed up the calculation of the dipole moment matrix elements, a threshold of 10 −12 to the eigen-coefficients was applied (see Yurchenko et al (2011)). We have also applied a threshold of 10 −8 Debye to the vibrational matrix elements of the dipole moment in order to reduce an accumulation error for higher overtones, see discussion by Medvedev et al (2016Medvedev et al ( , 2020. Table 1.…”

Section: Trove Specificationsmentioning

confidence: 99%

ExoMol line lists – XXXIX. Ro-vibrational molecular line list for CO2

Yurchenko

Mellor

Freedman

et al. 2020

Monthly Notices of the Royal Astronomical Society

130

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A new hot line list for the main isotopologue of CO2, 12C16O2 is presented. The line list consists of almost 2.5 billion transitions between 3.5 million rotation-vibration states of CO2 in its ground electronic state, covering the wavenumber range 0–20 000 cm−1 (λ > 0.5 µm) with the upper and lower energy thresholds of 36 000 cm−1 and 16 000 cm−1, respectively. The ro-vibrational energies and wavefunctions are computed variationally using the accurate empirical potential energy surface Ames-2. The ro-vibrational transition probabilities in the form of Einstein coefficients are computed using an accurate ab initio dipole moment surface with variational program TROVE. A new implementation of TROVE which uses an exact nuclear-motion kinetic energy operator is employed. Comparisons with the existing hot line lists are presented. The line list should be useful for atmospheric retrievals of exoplanets and cool stars. The UCL-4000 line list is available from the CDS and ExoMol data bases.

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The 2020 release of the ExoMol database: Molecular line lists for exoplanet and other hot atmospheres

Tennyson

Yurchenko

Al-Refaie

et al. 2020

Journal of Quantitative Spectroscopy and Radiative Transfer

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210

161

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The ExoMol database ( www.exomol.com ) provides molecular data for spectroscopic studies of hot atmospheres. While the data are intended for studies of exoplanets and other astronomical bodies, the dataset is widely applicable. The basic form of the database is extensive line lists; these are supplemented with partition functions, state lifetimes, cooling functions, Landé g-factors, temperature-dependent cross sections, opacities, pressure broadening parameters, k -coefficients and dipoles. This paper presents the latest release of the database which has been expanded to consider 80 molecules and 190 isotopologues totaling over 700 billion transitions. While the spectroscopic data are concentrated at infrared and visible wavelengths, ultraviolet transitions are being increasingly considered in response to requests from observers. The core of the database comes from the ExoMol project which primarily uses theoretical methods, albeit usually fine-tuned to reproduce laboratory spectra, to generate very extensive line lists for studies of hot bodies. The data have recently been supplemented by line lists derived from direct laboratory observations, albeit usually with the use of ab initio transition intensities. A major push in the new release is towards accurate characterisation of transition frequencies for use in high resolution studies of exoplanets and other bodies.

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Empirical normal intensity distribution for overtone vibrational spectra of triatomic molecules

Cited by 8 publications

References 48 publications

A semi-empirical potential energy surface and line list for H<sub>2</sub><sup>16</sup>O extending into the near-ultraviolet

A semi-empirical potential energy surface and line list for H<sub>2</sub><sup>16</sup>O extending into the near-ultraviolet

ExoMol line lists – XXXIX. Ro-vibrational molecular line list for CO2

The 2020 release of the ExoMol database: Molecular line lists for exoplanet and other hot atmospheres

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Empirical normal intensity distribution for overtone vibrational spectra of triatomic molecules

Cited by 8 publications

References 48 publications

A semi-empirical potential energy surface and line list for H&lt;sub&gt;2&lt;/sub&gt;&lt;sup&gt;16&lt;/sup&gt;O extending into the near-ultraviolet

A semi-empirical potential energy surface and line list for H&lt;sub&gt;2&lt;/sub&gt;&lt;sup&gt;16&lt;/sup&gt;O extending into the near-ultraviolet

ExoMol line lists – XXXIX. Ro-vibrational molecular line list for CO2

The 2020 release of the ExoMol database: Molecular line lists for exoplanet and other hot atmospheres

Contact Info

Product

Resources

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A semi-empirical potential energy surface and line list for H<sub>2</sub><sup>16</sup>O extending into the near-ultraviolet

A semi-empirical potential energy surface and line list for H<sub>2</sub><sup>16</sup>O extending into the near-ultraviolet