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R-matrix calculations on molecules of astrophysical interest using Quantemol-N

Varambhia, H.N.; (2010) R-matrix calculations on molecules of astrophysical interest using Quantemol-N. Doctoral thesis , UCL (University College London). Green open access

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We have carried out a series of ab initio R-matrix calculations at the static exchange and close-coupling levels of approximation on molecules of astrophysical interest. These include the polar triatomics HCN and HNC (hydrogen isocyanide) and their isotopologues DCN and DNC, the diatomics CS (carbon monosulphide) and SiO (silicon monoxide), the weakly polar CO molecule and the non-polar CH4 molecule. With the exception of CO, all the calculations presented here were carried out using the software ‘Quantemol-N’ which provides an intuitive user-friendly interface to the UK polyatomic R-matrix codes. A chapter is devoted to the discussion on the software: how to prepare an R-matrix calculation using it, its present capabilities and future development. The ultimate aim of this thesis is to demonstrate the need to account for electron-induced chemistry in any astrophysical model. We seek to show that in the case of polar molecules, namely, those molecules with large dipole moments, electron collisions are the dominant mechanism of rotational excitation in comets and other astrophysical bodies. Specifically, we will show that electron-impact excitation rate coefficients are several orders of magnitude higher than the corresponding atom-molecule ones. The thesis concludes with a summary of the key findings and opportunities (and where necessary improvements) that may arise from them. All the scattering equations presented here used atomic units.

Type: Thesis (Doctoral)
Title: R-matrix calculations on molecules of astrophysical interest using Quantemol-N
Open access status: An open access version is available from UCL Discovery
Language: English
UCL classification: 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/19432
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