ExoMol line lists – VIII. A variationally computed line list for hot formaldehyde

Al-Refaie, Ahmed; Yachmenev, Andrey; Tennyson, Jonathan; Yurchenko, Sergei N.

doi:10.1093/mnras/stv091

Cited by 65 publications

(43 citation statements)

References 80 publications

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“…These systems have been treated within the ExoMol framework19 and we refer the reader to the relevant publications for details of the ro-vibrational calculations51525354. Candidate ro-vibrational states were identified by sorting the files according to upper state energy.…”

Section: Resultsmentioning

confidence: 99%

Simulating electric field interactions with polar molecules using spectroscopic databases

Owens

Żak

Chubb

et al. 2017

Sci Rep

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Ro-vibrational Stark-associated phenomena of small polyatomic molecules are modelled using extensive spectroscopic data generated as part of the ExoMol project. The external field Hamiltonian is built from the computed ro-vibrational line list of the molecule in question. The Hamiltonian we propose is general and suitable for any polar molecule in the presence of an electric field. By exploiting precomputed data, the often prohibitively expensive computations associated with high accuracy simulations of molecule-field interactions are avoided. Applications to strong terahertz field-induced ro-vibrational dynamics of PH3 and NH3, and spontaneous emission data for optoelectrical Sisyphus cooling of H2CO and CH3Cl are discussed.

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Section: Resultsmentioning

confidence: 99%

Simulating electric field interactions with polar molecules using spectroscopic databases

Owens

Żak

Chubb

et al. 2017

Sci Rep

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“…A value of P max = 10 was used. This is a smaller value than used for previous Exomol line lists (Underwood et al 2016a;Sousa-Silva et al 2015;Owens et al 2017;Al-Refaie et al 2016, 2015b but with 12 degrees-of-freedom the basis set rapidly increases with increasing P . To estimate the converge of vibrational energies with this basis set we used a complete vibrational basis set (CVBS) extrapolation procedure similar to that described by Owens et al (2015).…”

Section: Variational Calculationsmentioning

confidence: 93%

ExoMol molecular line lists – XXVII. Spectra of C2H4

Mant

Yachmenev

Tennyson

et al. 2018

Monthly Notices of the Royal Astronomical Society

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A new line list for ethylene, 12 C 2 1 H 4 is presented. The line list is based on high level ab initio potential energy and dipole moment surfaces. The potential energy surface is refined by fitting to experimental energies. The line list covers the range up to 7000 cm −1 (1.43 µm) with all ro-vibrational transitions (50 billion) with the lower state below 5000 cm −1 included and thus should be applicable for temperatures up to 700 K. A technique for computing molecular opacities from vibrational band intensities is proposed and used to provide temperature dependent cross sections of ethylene for shorter wavelength and higher temperatures. When combined with realistic band profiles (such as the proposed three-band model), the vibrational intensity technique offers a cheap but reasonably accurate alternative to the full ro-vibrational calculations at high temperatures and should be reliable for representing molecular opacities. The C 2 H 4 line list, which is called MaYTY, is rmade available in electronic form from the CDS ExoMol XXVII: Line list for Ethylene 3 In this work we present new ab initio potential energy and dipole moment surfaces for ethylene and use them to compute a line list for elevated temperatures as part of the ExoMol database project (Tennyson & Yurchenko 2012; Tennyson et al. 2016). We name this line list MaYTY. Compared to the line list of Rey et al. (2016) we slightly increase the applicable frequency range and include many more weak transitions (50 billion here compared to 60 million previously) which are important for total opacity. Rovibrational energy levels were computed variationally using a refined PES with the TROVE program suite (Yurchenko et al. 2007; Yachmenev & Yurchenko 2015). Ethylene is the first 6 atom molecule in the Exomol database and the largest for which we have computed a line list so far. We also propose a new procedure for computing molecular opacities from vibrational transition moments only. Similar J = 0 approaches are very common in simulating spectra of large polyatomic molecules (Jornet-Somoza et al. 2012), where either very simple band profiles (e.g. Lorentzian) or sophisticated functional forms (such as the narrow band approach of Consalvi & Liu (2015)) are used. Here we develop a three-band model based on three fundamental bands of C 2 H 4 (one parallel and two perpendicular), which also represent its three dipole moment components. This J = 0-effort approach has allowed us to significantly extend the temperature as well as the frequency range of our line list and should be also useful for larger polyatomic molecules.The paper is organised as follows: In Section 2 we give details of our PES and DMS along with our variational calculations and how transition intensities were calculated. In Section 3 we give details of the MaYTY line list and compare with experimental data. The new procedure for generating opacities from vibrational band intensities is discussed in Section 4. We present conclusions in Sections 5. METHODS Potential Energy Surface and RefinementA...

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“…49 This has led to the computation of extensive line list of transitions for hot molecules by a number of groups. 19,[50][51][52][53][54][55] Recent work has particularly focussed on providing line lists for hot methane, 51,[56][57][58] the use of which has also been shown to have a dramatic effect on models of astronomical objects, 43 see Fig. 1.…”

Section: Uses Of Bound State Nuclear Motion Calculationsmentioning

confidence: 99%

Perspective: Accurate ro-vibrational calculations on small molecules

Tennyson

2016

The Journal of Chemical Physics

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In what has been described as the fourth age of quantum chemistry, variational nuclear motion programs are now routinely being used to obtain the vibration-rotation levels and corresponding wavefunctions of small molecules to the sort of high accuracy demanded by comparison with spectroscopy. In this perspective, I will discuss the current state-of-the-art which, for example, shows that these calculations are increasingly competitive with measurements or, indeed, replacing them and thus becoming the primary source of data on key processes. To achieve this accuracy ab initio requires consideration of small effects, routinely ignored in standard calculations, such as those due to quantum electrodynamics. Variational calculations are being used to generate huge lists of transitions which provide the input for models of radiative transport through hot atmospheres and to fill in or even replace measured transition intensities. Future prospects such as the study of molecular states near dissociation, which can provide a link with low-energy chemical reactions, are discussed. Published by AIP Publishing. [http://dx

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ExoMol line lists – VIII. A variationally computed line list for hot formaldehyde

Cited by 65 publications

References 80 publications

Simulating electric field interactions with polar molecules using spectroscopic databases

Simulating electric field interactions with polar molecules using spectroscopic databases

ExoMol molecular line lists – XXVII. Spectra of C2H4

Perspective: Accurate ro-vibrational calculations on small molecules

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