Electron continua from 3-60 keV Li+-Ne and Na+-Ne collisions

Abstract

Electron spectra from the Li+-Ne and Na+-Ne collisions have been measured for collision energies from 3.5 to 60 keV, ejection angles of 20-160 degrees , and electron energies in the 5-150 eV range. In both systems the electron spectrum consists of a relatively large continuum superimposed by discrete lines arising from doubly-excited atomic states. For the Li+-Ne system the continuum part decreases exponentially with electron energy, with a slope inversely proportional to the collision velocity. The angular distribution is approximately symmetric in the centre-of-mass system. For the Na+-Ne system the behaviour is more complicated, in particular, the continuum part cannot be fitted with a single exponential. The results are discussed in terms of recent models developed for one-electron systems by Solov'ev, Ovchinnikov and collaborators, describing the ionization process in terms of superpromotions, with the electron continuum being parametrized in terms of characteristic properties related to avoided and so-called hidden crossings of the quasimolecule.