Harald Schone

Dielectronic Excitation and Recombination in Crystal Channels

In previous papers, in this volume, electron-ion recombination processes have been studied using either free-electron targets or targets of “almost-free” electrons which are loosely bound to atoms or molecules. In the former case, the techniques generally involve either merged electron-ion beams in “single-pass” configuration or in electron “coolers” in storage rings or observation of photons and associated charge state fractions in electron beam ion sources, in either the EBIS or EBIT configuration. These techniques are direct and, in the case of merged or crossed beam experiments, offer very high energy resolution.

Charge and angular correlated inelasticities in MeV/nucleon ion-atom collisions

Using an Elbek high-resolution magnetic spectrograph, we measured energy loss an angular distributions of MeV/nucleon projectile ions in coincidence with target recoil-ion charge state. We investigated collisions of 10 and 20 MeV C/sup 6 +/ on He, Ne, Ar, and Kr where the target atom is multiply ionized and the projectile emerges in charge state q or q-1. The amount of energy transferred to the continuum electrons exceeds, by far, the sum of the values of the ionization potentials and shows a strong target Z dependence. Both an n-body classical-trajectory Monte Carlo method (nCTMC) and an energy deposition model are used for comparison with the experimental data. 12 refs., 3 figs.

Excitation curve for Auger decay of the (1s2s2p2)3D state of C2+ formed through RTE☆

Abstract The ORNL EN tandem supplied beams of 3.5–9 MeV C 3+ ions which were incident on a differentially pumped He target. Auger electrons emitted by fast C 2+ ions emerged at 10° (lab) w.r.t. the incident ion beam. They were detected using a two stage spectrometer with kinematic refocusing. An excitation curve was obtained for the (1s2s2p 2 ) 3 D state Auger decay to the ground state of C 3+ . The excitation curve peaks at ~ 6 MeV, which strongly supports the notion that the state is formed through resonant transfer and excitation.

Electron emission from 3.0 MeV Br-Kr collisions

Abstract The electron emission spectra observed following low-MeV collisions of heavy ions with heavy atoms are often dominated by electrons with a continuous range of energies. For example, the electron emission spectra from Kr-Kr and Kr-Xe collisions are dominated by a continuous portion that extends from low energies to nearly 1000 eV. For the Kr-Kr case, there is evidence that the continuous portion of the spectrum results from the emission of 20–24 electrons from the two-ion system prior to the time L-Auger emission takes place and that many of the emitted electrons have energies in the range of 25–500 eV. The present data were obtained for the closely related Br-Kr system with a high-resolution electron spectrometer to see whether discrete lines could be resolved and if they could, whether they would comprise the major portion of the spectrum or appear as lines superimposed upon the continuum. The experiment resolved only a few peaks and they appear to be superimposed upon a continuum of different origin.

Transfer and excitation processes studied in H-like S and Li-like and H-like F colliding with H2

Abstract We have studied transfer and simultaneous excitation by three different experimental techniques. Coincidences between two K X-rays were measured for S15+, as well as coincidences between one K X-ray and the charge-exchanged projectile for Li-like F and projectile Auger electrons for H-like F, in each case colliding with H2. For all three collision system, the measured cross sections are dominated by resonant transfer and excitation (RTE). Also, for the F projectiles, strong contributions from two-electron transfer and excitation (2eTE) were found.