Dr Candadi V Sukumar

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.