Experimental and theoretical velocity distributions of electrons ejected in l -6 keV ionizing H"-H collisions are presented. Both the experimental velocity distributions and the relative total ionization cross sections can be explained by the theory in a fully consistent~ay. Strong evidence is found for the existence of a saddle-point ionization mechanism at collision energies of 4 keV and higher.A very fundamental problem in atomic collision physics is ionization in ion-atom systems. The continuum distribution of electrons ejected in such collision systems is still not completely understood, neither theoretically nor experimentally, particularly at low (keV) impact energies,~here the collision dynamics possesses a molecular character. Recently, one of the most surprising theoretical predictions was the existence of a so-called "saddle-point ionization mechanism. " Saddle-point electrons were revealed in classical trajectory Monte Carlo

No abstract

No abstract

No abstract

This article reviews experimental photoemission cross sections in the extreme ultraviolet, for transitions in excited atoms and atomic ions formed in electron collisions with atoms and molecules. A survey of the available experimental data for each investigated target gas reveals severe inconsistencies between cross sections reported by different laboratories. As almost all reported cross sections are based on relative measurements, a detailed discussion is given of the methods used for normalization of the cross sections.