Owens, AT;
(2017)
Variational calculations of rotation-vibration spectra for small molecules of astrophysical interest.
Doctoral thesis , UCL (University College London).
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Abstract
Variational calculations of rotation-vibration spectra are presented for a range of four- and five-atom molecules of atmospheric and astrophysical importance. Using state-of-the-art electronic structure methods, new nine-dimensional potential energy and dipole moment surfaces are constructed for methyl chloride (CH3Cl), silane (SiH4), and methane (CH4). The respective surfaces are rigorously evaluated against high-resolution spectroscopic data from a variety of experimental sources. The ab initio potential energy surfaces represent some of the most accurate to date, whilst intensity simulations utilizing the dipole moment surfaces show good agreement with experiment. A novel application of rotation-vibration computations is introduced to investigate the sensitivity of spectral lines to a possible space-time variation of the proton-to-electron mass ratio μ. The approach relies on finding the mass dependence of the computed energy levels and is only possible because of the remarkable accuracy of variational calculations. Highly sensitive transitions are uncovered for ammonia (NH3) and the hydronium cation (H3O+) which could lead to a tighter constraint on a varying μ. An advantage of the variational approach is that Einstein A coefficients can be determined to help guide future laboratory and astronomical observations. This thesis demonstrates the current capabilities of variational calculations of rotation-vibration spectra and highlights the challenges faced by the field.
Type: | Thesis (Doctoral) |
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Title: | Variational calculations of rotation-vibration spectra for small molecules of astrophysical interest |
Event: | UCL (University College London) |
Open access status: | An open access version is available from UCL Discovery |
Language: | English |
Keywords: | Molecular Spectroscopy, Quantum Chemistry, Exoplanets |
UCL classification: | UCL UCL > Provost and Vice Provost Offices UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy |
URI: | https://discovery.ucl.ac.uk/id/eprint/1556260 |
1. | United Kingdom | 11 |
2. | United States | 8 |
3. | Australia | 3 |
4. | Sweden | 2 |
5. | Turkey | 2 |
6. | Germany | 2 |
7. | South Africa | 2 |
8. | Russian Federation | 2 |
9. | France | 1 |
10. | Ireland | 1 |
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