Dr Candadi V Sukumar

Abstract:

Semiclassical and exact quantum methods have been used to calculate the positions and residues of Regge poles for two interatomic potentials. A Lennard-Jones (6,4) potential with parameters approximating H+-Ar collisions and a Lennard-Jones (12,6) potential with parameters approximating the elastic scattering of K by HBr have been used. There is good agreement between the semiclassical and quantum calculations both for the pole positions and modulus and phase of the residues. Some properties of Regge trajectories for the Lennard-Jones (12,6) potential are also investigated.

Abstract:

A variational principle for the position of Regge poles in potential scattering is derived and applied to two problems, one of which provides a model for elastic e-Ar scattering. Direct numerical techniques are applied to a potential representing p-Ar collisions and the results are compared to recent JWKB calculations.

Abstract:

The usefulness of complex angular momentum techniques is examined in the context of low-energy atomic collisions. For elastic e-Ar collisions at energies between 50 eV and 200 eV the observed structure in the differential cross sections is reproduced by the contribution from three Regge poles. For a Lennard-Jones potential representing p-Ar collisions the contributions from many poles are significant and the interference between these contributions leads to serious numerical difficulties in the application of the Watson-Sommerfeld transformation. The Remler model is shown to give a reliable phenomenological procedure for fitting measured differential cross sections for ion-atom collisions, even though the physical basis of the model is questionable.

Abstract:

Complex coordinates are used in the development of a variational principle for Siegert resonant states. The principle is first tested by application to a potential scattering problem. The position and width of the lowest 1S resonance in e-H scattering are calculated to be 9.557 eV and 0.048 eV respectively. The corresponding values for the lowest 2S resonance of He- are 19.398 eV and 0.012 eV.