Investigation of the dynamics of dissipative U+Au collisions with δ-electron spectroscopy

Abstract

δ-electron emission in elastic and dissipative collisions of U+Au at E/A = 8.65 MeV has been investigated. The velocity vectors of the reaction products were measured in coincidence with electrons of energies up to 3.2 MeV. The δ-electron yield measured for elastic collisions is in good agreement with coupled-channels calculations. The δ-electron spectra of dissipative reactions show a clear dependence on the violence of the collision, i.e. the total kinetic energy loss (TKEL). The shape of the spectra are analysed with an atomic model by a fitting procedure using phenomenological trajectories. The results indicate an increasing contact time of the united system with increasing total kinetic energy loss reaching 1.16(4) × 10 −21 s at < T KEL > = 375 MeV.

6 Modern Electron and Positron Spectrometers – Selected Aspects of a Broad Field

“…In the latter version the spectrometer has been equipped with scintillator-type focal detectors and was operated in combinations with large area PPAC's to allow the determination of heavy-ion three-body kinematics after fission. The experiment was devoted to the measurement of collision delays due to nuclear interaction in the order of 10 ~ 20 s which may lead to interference-like modifications in the (5-electron spectrum [44,43], At the high energies where these effects occur the cross section for creation of ^-electrons is comparably low, as it is for positrons at lower positron energies.…”

“…The Double-Orange in the above version is employed for the investigation of narrow electron-positron pair lines observed in the LS after heavy-ion collisions in coincidence with ejectiles, with scattered projectiles or with fission fragments [45a, 45b, 41a, 41b], Similarly equipped Single-Orange versions have been applied for positron spectroscopy after heavy-ion collisions in the search for quasi-atomic QED effects [42,40] as well as for the investigation [44] of <5-rays at higher energies (up to 2.5 MeV). In the latter version the spectrometer has been equipped with scintillator-type focal detectors and was operated in combinations with large area PPAC's to allow the determination of heavy-ion three-body kinematics after fission.…”

“…If necessary, the positrons can also be identified by their annihilation radiation. The measurements performed with the TORI spectrometer focussed on studying nuclear collision dynamics with electrons and positrons [43,44].…”

Search for a long lived component in the reaction U+U near the Coulomb barrier

“…J. Stroth et al have investigated the collision system U+Au at 8.65A MeV [11]. So called "ternary events" where the Au-nucleus survives and the U-nucleus is fissioning after the collision, have been discussed.…”