Exploring collisional processes in astrophysical environments: From quantum dynamics to spectroscopy

by Dr Deboki Reja (Postdoctoral Researcher, Uppsala University)

Wednesday 30 Sept 2026, 13:30 → 14:30 Europe/Stockholm

FC 61 (AlbaNova Main Building)

The collisions among atoms, ions, and molecules are fundamental processes in the universe.  They can occur through a variety of elastic and inelastic processes, including electronic, vibrational, and rotational excitation, charge transfer through electron exchange, and chemical reactions leading to the formation of new species.  These processes affect the spectral lines of atoms, ions, and molecules, thus playing a significant role in the analysis of spectra from astrophysical objects.  A thorough understanding of these processes and the ability to perform accurate calculations are vital for achieving accurate measurements of stellar properties.

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 are coupled through radial, rotational, spin-orbit coupling, and transition dipole moments.  In such cases, the dynamics evolve on coupled potential energy surfaces, imposing theoretically and computationally challenging tasks. The resulting cross sections and rate coefficients provide the link between the underlying quantum dynamics and observable astrophysical phenomena.

The talk will highlight three applications: charge transfer of O⁺ with neutral atoms and their importance for understanding the chemical and spectroscopic evolution of SN 1987A, ion-molecule collisions involving H⁺ + CO/O₂, and the role of Ca-H₂/H collision in shaping spectral line profiles in M-dwarf atmospheres.