Complete break up of the lithium atom by electron impact

A simplified qualitative model based on the shake-off mechanism framework is proposed in the first Born approximation to study the triple ionization (e, 4e) process of the Li atom by fast electron impact in a coplanar geometry. The recent experiment of Wehlitz et al (1998 Phys. Rev. Lett. 811813), on the triple photo ionization (gamma, 3e) of the Li atom has stimulated us to study the above (e, 4e) process for low momentum transfer ((Q) over right arrow) and for high incident energy, since in the dipolar limit (Q) over right arrow --> 0, the results for (e, 4e) should converge to the corresponding (gamma, 3e) results. The model proposed is particularly suitable for low momentum transfer as well as for asymmetric kinematics with respect to the electrons in different shells. The fully differential (spin averaged) cross sections (7DCS) with respect to the angular distributions of the shake-off electron, which in the present model is assumed to be the valence electron of the Li atom, are studied. 7DCS is also studied for the second electron ejected from the Is shell for some selective kinematics. The peak values of the 7DCS versus incident electron energy curves for a given set of kinematics qualitatively compare well with the experimental findings of Wehlitz et al. To the best of our knowledge, this is the first theoretical work performed relating to the 7DCS calculation of the (e, 4e) process of the Li atom.