arXiv 0802.16772008-02-12physics.atom-ph

电子偶素-氢碰撞中负氢离子的形成

Formation of negative hydrogen ion in Positronium - Hydrogen collisions

S. Roy snd C. Sinha

备注：: 16 pages, 10 figures

摘要：

本文从理论上研究了电子偶素（Ps）的激发态在负氢离子（H^-）形成截面（微分截面和总截面）中的重要性。例如，在一个实施例中，阈值-500eV）。计算是在一个定性模型的框架内进行的，碰撞后库仑修正的Eikonal近似（CMEA）。并对基态和激发态的捕获进行了比较研究。本CMEA模型考虑了高阶效应，这对于第一玻恩型近似（库仑玻恩的离子情况下）不应该是足够的重排过程是必不可少的。在低入射能量下，Ps（2s，2 p）的激发态在H^-形成截面中起主导作用.即使在非常高的入射能量下（例如，Ei = 500 eV），表明高阶效应的重要性。在高入射能量下，目前的CMEA微分截面（DCS）表现出双峰结构，这在CBA中完全不存在，并且可以再次归因于高阶效应。

英文摘要：

The importance of the excited states of Positronium (Ps) in the formation cross sections(both differential and total) of the negative hydrogen ion (H^-) are investigated theoretically for the charge transfer reaction, Ps (n = 1, 2) + H --> e+ + H^- for a wide range of incident energies (e. g., threshold - 500 eV) . The calculations are performed in the frame work of a qualitative model, the post collisional Coulomb Modified Eikonal Approximation (CMEA) . A comparative study is also made between the capture from ground and excited states of the Ps. The present CMEA model takes account of higher order effects which is essential for a rearrangement process where the First Born type Approximation (Coulomb Born for the ionic case) is not supposed to be adequate. At low incident energies, the excited states of Ps (2s, 2p) are found to play a dominant role in the H^- formation cross sections . Significant deviations are noted between the present CMEA and the Coulomb Born (CBA) results even at very high incident energies (e.g., Ei = 500 eV), indicating the importance of higher order effects. At high incident energies the present CMEA differential cross section (DCS) exhibits a double peak structure which is totally absent in the CBA and could again be attributed to higher order effects.

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