Title:  Investigation of the Dynamics of Collisional Processes in Atomic and Molecular Systems

Speaker: Prof. Alisher Kadyrov, Curtin University, Australia

Time: 15:00, Dec. 15 (Monday), 2025

Place: Room 666, Building 5

Abstract: 

The physics of quantum collisions is fundamental to our understanding of the universe at its most basic level. In particular, accurate knowledge of ion-atom and ion-molecule collisions is essential for practical applications such as development and maintenance of fusion reactors, hadron therapy of cancerous tumours, and astrophysics. Currently, there is an urgent demand for accurate collisional data for these applications. Several methods have been developed to meet the demand. However, solving the collision problem accurately and in a kinematically complete fashion has remained an insurmountable problem. Addressing this challenge required fundamental advancement of the underlying quantum collision theory as the conventional many-body scattering theory is formally valid only when the particles interact via short-range potentials. We have developed a new surface-integral formulation of scattering theory that is valid for both short-range and long-range Coulombic potentials. It provides the post form of the breakup amplitude for charged particles absent in the conventional scattering theory.  Based on the new formulation of scattering theory we have developed a number of practical ab initio approaches capable of modelling atomic collisions. One of them, known as the wave-packet convergent close-coupling (WP-CCC), has thus far provided some of the most accurate cross sections for all interconnected atomic collision processes taking place in a fusion reactor. We start this talk with a brief overview of the WP-CCC method. The method is based on expansion of the total scattering wave function using a two-centre basis made of wave packets discretising the continuum. The exact many-body Schrödinger equation is converted into a set of coupled-channel differential equations for unknown expansion coefficients. In the asymptotic region, these coefficients represent transition amplitudes for all processes including elastic scattering, excitation, ionisation, and charge exchange. The WP-CCC method accurately solves the scattering problem by systematically increasing the size of the calculations until the results converge. We present results for integrated total and state-selective cross sections for various processes taking place in fusion plasma. We also present all types of the singly and doubly differential cross sections, as well as the fully differential cross section for ionisation.