(e,e'f) Coincidence experiments on 235U and 238U

Abstract. Electromagnetic fission of 23Su projectiles at E/A = 600 and 1000 MeV was studied with the ALADIN spectrometer at the heavy-ion synchrotron SIS. Seven different targets (Be, C, A1, Cu, In, Au and U) were used. By considering only those fission events where the two charges added up to 92, most of the nuclear interactions were excluded. The nuclear contributions to the measured fission cross sections were determined by extrapolating from beryllium to the heavier targets with the concept of factorization. The obtained cross sections for electromagnetic fission are well reproduced by extended Weizs~icker-Williams calculations which include E1 and E2 excitations. The asymmetry of the fission fragments' charge distribution gives evidence for the excitation of the double giant-dipole resonance in uranium.

“…[29] which are in good agreement with other measurements [23,[30][31][32]. Furthermore, we used the parametrizations for the isoscalar component of the GQR from Ref.…”

Section: Calculationsmentioning

confidence: 53%

“…Furthermore, we used the parametrizations for the isoscalar component of the GQR from Ref. [31] and for the isovector component from…”

Section: Calculationsmentioning

confidence: 99%

Electromagnetic fission of238U at 600 and 1000 MeV per nucleon

Rubehn

Müller

Bassini³

et al. 1995

“…At low energies near the fission barrier photofission experiments have provided unique information on barrier parameters and the spectrum of transition states [3]. Furthermore the fission probabilities and fragment mass splits in the fission decay of different Giant Resonances have been studied in (e, e~f)-coincidence experiments [4]. In the energy range between the Giant Dipole Resonance (GDR) and the pion threshold (Ethr.…”

Section: Introductionmentioning

confidence: 99%

Photofission of235U and238U at intermediate energies: absolute cross sections and fragment mass distributions

Frommhold

Steiper

Henkel

et al. 1994

Self Cite

Abstract. The total photofission cross section c%,F for Z35U and 238U has been measured in the energy range 50< E.y < 800 MeV at the 855 MeV Mainz Microtron MAMI using energy and time tagged photons (Glasgow Tagger) and a 47r arrangement of position sensitive fragment detectors. Besides the absolute photofission cross section c%,F, which almost completely exhausts the total photon absorption cross section for these nuclei, fragment mass distributions in this energy domain were determined via time of flight techniques (TOF). The results for the total photofission cross sections c%,F normalized to the atomic number A for both isotopes coincide, and agree in the A-resonance region, within the systematic errors, with the socalled "Universal Curve" C%,T/A of the total photon absorption cross section crT,T. At higher energies the cross sections exhibit a smooth behaviour. In particular, it is shown for the first time that there is n__0o resonancelike shape near the D13 resonance (at ~ 710 MeV) as observed for the free proton. This complete suppression of the DI3 resonance in complex nuclei is not yet understood on a microscopic level. The fragment mass distributions show a predominantly mass symmetric fission. However, contributions from mass asymmetric fission at some photon energies may give a hint of an increased mass asymmetric fission after the onset of the pion and two pion channels.

Few-neutron removal from238U at relativistic energies

Aumann

Sümmerer

Geißel

et al. 1995

Abstract. As part of a comprehensive study of uranium fragmentation at relativistic energies at the GSI projectile fragment separator, FRS, inclusive neutron-removal cross sections have been measured for several zr~ channels at projectile energies of 600 and 950 A MeV using targets of A1, Cu and Pb. The variation of the experimental cross sections with target nuclear charge is used to disentangle nuclear and electromagnetic contributions. The electromagnetic cross sections agree surprisingly well with a simple harmonic oscillator calculation of giant dipole resonances based on measured photonuclear cross sections and do not require an extra enhancement of the two-phonon giant dipole excitation as concluded from similar measurements with 197Au.