Electron-impact dissociation and transient properties of a stored LiH2- beam

The fragmentation of LiH2- anions after electron impact was investigated at the heavy-ion storage ring TSR (Max-Planck-Institute in Heidelberg, Germany). The main reaction channel was found to be electron detachment followed by a breakup into LiH + H. In the first ms after production of the molecular ions in a cesium sputtering ion source, additional contributions were observed in the Li + H2 and Li- + H2 channels, hinting at an initial population of a short-lived state of the anion. To gain a better understanding of the mechanisms underlying the observed behavior of the system, ab initio calculations of relevant potential energy surfaces were performed at selected geometries. The experimental findings are discussed in the light of these calculations. (authors)