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

We have measured the energy spectra of electrons emitted by the photoexcited 2p-'n&! inner-shell states of argon. The photon bandwidth and, to a lesser extent, the elemonenergy resolution are improved as compared with earlier measurements of Meyer and coworkers. ?his allows a more detailed comparison with recently calculated decay probabilities.Additionally, we have measured the elemon-energy specmm perraining to the decay of the 2pG;Sd inner-shell excited state, but the observed decay channels are not in good agreement with the calculations.