Seminar: Collisions in astrophysical environments

The collisions among atoms, ions, and molecules are fundamental processes in the universe. These collisions occur through various elastic and inelastic processes including: (i) the excitation of partners (electronic, vibrational, rotational excitations), (ii) charge transfer through the exchange of electrons, and (iii) reactions that result in the formation of new species. These processes affect the absorbing and emitting spectral lines of atoms, ions, and molecules, thus playing a significant role in the analysis of the spectra of astrophysical objects. A thorough understanding of these processes and the ability to perform accurate calculations are vital for achieving accurate measurements of stellar properties, particularly abundances. The detailed calculations of these inelastic collision processes involve intricate atomic and molecular structure calculations to generate wave functions and potential energies needed for performing effective dynamics calculations. Often, these inelastic processes occur through non-adiabatic interactions, which results in the breakdown of the Born-Oppenheimer approximation. In such cases, the dynamics evolve on coupled potential energy surfaces, imposing theoretically and computationally challenging tasks.

I will talk about the effect of collisional broadening and inelastic processes in the stellar spectra and their importance. I will also present an overview of the electronic structure calculations and non-adiabatic interactions followed by theories of collision dynamics.

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We shall leave for lunch to Rullan at around 12:15. There will be fika after the seminar.