Partitioning of Momentum in Electron-Impact Double Ionization of Magnesium

Electron-impact double ionization of magnesium has been observed in an (e,(3-1)e) experiment. A 1.0-keV incident electron is used and two 100-eV ejected electrons are observed in coincidence. The scattered electron is not detected so that the cross section is integrated over all values of momentum transfer. A preference is observed for both target electrons to be ejected in the forward direction. In contrast to single ionization in the same energy regime, it is found that from 1 to more than 5 a.u. of momentum may be imparted to the ion core in the doubly ionizing collision.