Banuary, Mwdansar2024-02-282024-02-282024ROLL NO.166122103https://gyan.iitg.ac.in/handle/123456789/2557Supervisor: Gupta, Ashish KumarThis thesis focuses on the application of modified smooth exterior scaling (MSES) as an efficient method to impose outgoing boundary conditions in e-atom and e-molecule scattering resonances. This is the first time that the MSES method has been applied to calculate energies and widths of Auger and shape resonances in three-dimensional many-body electron systems. MSES converts the divergent resonance wave functions into square integrable ones thereby making the study of temporary bound states (resonance states) amenable to bound state electronic structure methods. The main objective of this thesis is to formulate the MSES method in bivariational SCF and electron propagator methods.enThesis