Executive Summary : | Resonance states are crucial in the structure of atoms and molecules, as they manifest in the scattering of sub-systems with large cross sections. When an atomic system is embedded in a plasma, low-lying resonance structures lead to the resonant radiative recombination (RRR) process, which dominates over recombination rates in the energy regime for which electron wavelength exceeds the potential range. These resonance states also play a key role in threshold electron-dynamics, leading to drastic changes in threshold photoionization, electron-impact ionization, and excitation. Determining the energy and width (life time) of resonance states in atomic systems is a challenging task. Several studies have reported on resonance states in various atomic and molecular systems in vacuum in recent decades. However, most investigations have used either the Debye-Huckel model of screening or a modified Debye-Huckel model of screening. In dense plasmas, non-ideality is essential for understanding phenomena associated with plasma physics, inertial fusion, astrophysics, exploding wires, x-ray free electron laser, and condensed matter. Quantum mechanical effects of diffraction and symmetry are also important in dense plasmas. This project proposes to study the effects of non-ideality (NI) and quantum mechanical diffraction of dense plasmas on resonance states in electron-hydrogenic systems and positron-hydrogenic systems. The study will use two screening models: one considering the NI of plasma and the other considering the quantum mechanical effects of diffraction. The primary concern will be H, He+, and Ps, which are of utmost interest in various astronomical investigations. |