Evaluation of Quasi-Molecules for collision studies at low energies

Slow collisions involving ions and atoms or molecules has wide application from astro to plasma physics [1] and require special attention for obtaining accurate information regarding its structure and interactions. At low velocities the projectile can reach the close vicinity of the target for forming a quasi-molecule. The accurate determination of its eigenvalues and eigenfuctions poses difficulties when the internuclear separation becomes less than 1 bohr. We report the details of our recent study on (SiH)3$+$ quasi-molecule using the multi-reference single- and double-excitation configuration interaction (MRD-CI) method [2]. \\[4pt] [1] B.H. Bransden amd M.R.C. McDowell. Charge Exchange and the Theory of Ion-Atom Collisions(Clarendon Press, Oxford, 1992).\\[0pt] [2] R. J. Buenker, Current Aspects of Quantum Chemistry 1981, Vol \textbf{21}, edited by R. Carbo (Elsevier, Amsterdam) p 17.