Abstract
In the universe, new galaxies are formed in interstellar clouds of molecules and dust particles that condense locally under the influence of gravity to form proto-stars. Once a star has formed, protoplanetary disks emerge which are the nurseries where new planets are born. Information about the molecular composition, density, temperature, etc., of protoplanetary disks can be obtained from molecular spectra measured using space telescopes like the fairly recently launched James Webb Space Telescope (JWST).
Researchers use models to extract the desired information from these spectra. Important parameters required by these models include the rates of transitions between different energy states of molecules such as CO2, H2O, HCN, C2H2, which arise from collisions with the most common atoms and molecules: helium (He) and hydrogen (H2).
This PhD thesis describes the development of new quantum-mechanical computational methods and algorithms that can be used to calculate the required rate constants accurately and efficiently. These methods have been tested and applied to different vibrational-rotational states of CO2, an important molecule in this context, in collisions with He atoms. The results obtained are now available to astrophysicists and astrochemists for use in their models which are important not only to extract the desired information from the measured spectra, but also to understand, using simulations, how protoplanetary disks evolve into planets. Our results can also be used in interpreting spectra of the atmospheres of other planets and exoplanets.
