Single electron capture and ionization involving atomic (and molecular) hydrogen and helium at low intermediate impact energies.

摘要

Single electron capture from atomic (and molecular) hydrogen by 0.32, 0.5 and 0.75 a.u. Ar8+ ions, and electron ejection from atomic hydrogen by 0.775, 1 and 1.415 a.u. protons and from helium by 0.895 to 2 a.u. protons were studied. Proton impact on helium experiments were done to close an existing energy gap studied in this system. Atomic hydrogen bombarded by a proton forms a true three body system which makes our ionization experiments involving atomic hydrogen unique. They are the first set of experiments which provide ejected electron momenta that can be compared without theoretical compromise to existing theories. Because hydrogen normally exists in nature as H₂, it must be dissociated to obtain H. We have built a hydrogen source that dissociates molecular hydrogen used in both of the hydrogen experiments. This source consists of a discharge tube in a microwave cavity. The technique used for all these experiments is momentum imaging spectroscopy, whereby the partners of the collisions are detected in coincidence. From the electron-capture experiments, energy-gain information was extracted, which allowed us to determine into which states of the projectile ion the electron was captured. We obtained and compared results of atomic and molecular hydrogen targets. Our results showed that the electron was captured into the n-states expected from theory, but not in the ratios that were predicted. From our single ionization experiments involving both helium and atomic hydrogen targets, we were able to extract the ejected electron momentum spectra for different impact energies.