Dr Candadi V Sukumar

Abstract:

Semiclassical and exact quantum methods have been used to make the first calculations of Regge pole positions and residues for singular complex optical potentials. The semiclassical pole positions are in excellent agreement with the quantum results. The semiclassical residues are less accurate, especially for the leading pole, but their accuracy rapidly improves as the pole number increases.

Abstract:

A differential equation in momentum space is derived for the case of an attractive Coulomb potential. The bound-state energies and the momentum eigenfunctions are shown to arise from this differential equation in a simple fashion. The zero-energy partial-wave momentum eigenfunctions are also derived. The s-wave bound states and their momentum eigenfunctions in a three-dimensional linear potential and an attractive 1/(r+ beta ) potential are derived by similar techniques. The connection between the quantisation formulae in these potentials and the classical action integral in momentum space is explored.

Abstract:

The method of complex coordinates is a useful tool for studying many bound-free transitions. Recently the method has been used to calculate photoabsorption cross sections of one- and two-electron atoms. The authors have performed calculations on the photoabsorption of lithium and sodium by the complex-coordinate method using different pseudopotentials. The results from the different pseudopotentials are compared with other theoretical and experimental results.

Abstract:

The authors are concerned with relatively simple semi-empirical models for quenching of excited atoms by stable molecules, i.e. the transfer of electronic energy into vibrational and translational degrees of freedom. The most notable example is the quenching for Na(33P) to the ground state by N 2. The cross sections are first related to those for free-electron-molecule scattering in a 'first-order' theory and it is shown that this simple theory leads to numerical values which are far too small. Thus the authors invoke an ionic collision complex formed by partial charge transfer and succeed in obtaining reasonable total cross sections and final-state branching ratios from a hybrid theory. Calculations are carried out for excited Li, Na and K colliding with H2, N2 and O2.

Abstract:

A model assuming simple analytical forms for potential curves and coupling matrix elements is used to interpret the experimental results on preionisation and predissociation of NO via high-lying molecular states of NO. Information regarding the potential energy curves for the high-lying molecular states are obtained from the model.