Charge Transfer in Negative Ion Collisions

Electron detachment is an important inelastic process for negative ion collisions. Because of the large number of electrons produced by electron loss, charge transfer to the target atom or molecule becomes a likely event, whereas in positive ion collisions it is virtually nonexistent. This mechanism is manifested in the formation of temporary negative ions of the target, usually in the form of autodetaching excited states. Electron spectroscopy of the ejected electrons produced during the collision allows one to observe lines which can be identified to specific negative ions. The position, width and relative intensity of these lines can be related to the structure of the negative ion. Examples of collisions involving H- with heavy rare gas atoms and molecular nitrogen will be discussed.