Electron-capture-to-continuum cusp inU88++N2collisions

Abstract

For the collision system U88+ + N2 at a collision energy of 90 MeV/u, the energy distribution of electrons being nonradiatively captured from the target into the projectile continuum has been measured under an angle of 0° with respect to the projectile beam axis. This measurement of the electron-capture-to-continuum cusp with the highest effective projectile charge Z f = 88 at a near-relativistic collision velocity of f « 0.41 is shown to be characterized by a strong asymmetry in the cusp shape. By comparing the data to measurements of the radiative-electron-capture-to-continuum cusp for the same collision system, the opposite asymmetry of the cusp is traced back to the varying underlying mechanisms. The experimental results are compared with the two theoretical calculations available for this process, one of them in the semirelativistic impulse approximation and the other in the nonrelativistic continuum-distorted-wave approach. A corresponding fully relativistic treatment may be motivated by the presented experimental data.

Strong asymmetry of the electron-loss-to-continuum cusp of multielectronU28+projectiles in near-relativistic collisions with gaseous targets

“…More recently (see Ref. [21]) relativistic kinematics were implemented in order to take into account high collision velocities.…”

“…Corresponding spectra can be accessed by measuring the electron cusp, i.e., the energy distribution of electrons emitted under an angle of ϑ e ≈ 0 • with respect to the projectile beam and having a velocity similar to the projectile velocity [2,[10][11][12][13][14][15][16][17][18]. Deviations from a symmetric cusp shape measured in the laboratory frame-of-reference can be traced back to an anisotropic electron emission in the projectile frame [19][20][21][22].…”

“…Measured and calculated energy spectra of cusp electrons for the collision systems U 28+ + H 2 at 50 MeV/u, U 28+ + N 2 at 30 MeV/u, and U 28+ +Xe at 50 MeV/u are presented. Unprecedentedly clean experimental conditions were facilitated by using the magnetic forward-angle electron spectrometer [19][20][21][22] installed in the experimental storage ring ESR of the heavy-ion accelerator facility GSI Helmholtzzentrum für Schwerionenforschung. The measured spectra are compared with theoretical calculations based on first-order perturbation theory applying relativistic wave functions for the initial bound states of the heavy multielectron projectile, and the observed discrepancies between experiment and theory are discussed.…”

Search for bound-state electron+positron pair decay

“…Monochromatic positrons emitted by fast projectiles is a favourable background-free detection method. Detection of ∼ 11-keV positrons is feasible with an electronspectrometer installed at the ESR [58,59]. The concept of detecting positrons is described in detail in [60].…”

Physics book: CRYRING@ESR

“…As was predicted theoretically by Jakubassa-Amundsen ( 2003) and confirmed experimentally by D R A F T 2.2. Atomic collisions dynamics 31 Hillenbrand et al (2015), RECC is competing with the non-radiative electron capture to the continuum (ECC) process where an initial target electron is transferred to the projectile continuum. It was shown that the cross sections of both processes are comparably large for a nitrogen target at 90 MeV/u.…”