Slow Collisions of Si3+ with Atomic Hydrogen

Low energy electron capture from hydrogen atom by multi-charged ions continues to be of interest and applications include both magnetically confined fusion and astrophysical plasmas. The charge exchange process reported here\textit{, Si}$^{3+} + H$ $\rightarrow $ \textit{Si}$^{2+} + H^{+}$ is an important destruction mechanism of Si$^{3+}$ in photo-ionized gas. The soft X-ray emission from comets has been explained by charge transfer of solar wind ions, among them Si$^{3+}$, with neutrals in the cometary gas vapor. The state selective cross sections are evaluated using the full quantum [1] and semi-classical molecular orbital close coupling (MOCC) [2] methods. Adiabatic potentials and wave functions for a number of low-lying singlet and triplet states of and symmetry are calculated wing the MRD-CI package [3]. Details will be presented at the conference. \\[4pt] [1] L. B. Zhao, D. C. Joseph, B. C. Saha, H. P. Liebermann, P. Funke and R. J. Buenker, Phys. Rev A, \textbf{79}, 034701 (1009).\\[0pt] [2] M. Kimura and N. F. Lane, At. Mol. Opt. Phys \textbf{26}, 79 (1990).\\[0pt] [3] R. J. Buenker, ``Current Aspects of Quantum Chemistry 1981, Vol \textbf{21}, edited by R. Carbo (Elsevier, Amsterdam) p 17.