C"+_6_0 + C_6_0 collisions. Pt. 1 Multifragmentation and collective flow effects

SIGLEAvailable from TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Collective motion in Ar+Pb collisions at beam energies between 400 and 1800 MeV/nucleon

SIGLEAvailable from TIB Hannover: RO 801(91-26) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

The Gamow-Teller decay of "1"0"5Sn to three-particle states in "1"0"5In

The EC/#beta#"+ decay of "1"0"5Sn was reinvestigated by using "5"8Ni (5 MeV/u) + "5"0Cr reactions, chemically selective on-line mass separation and #gamma#-ray spectroscopy. The half-life of "1"0"5Sn has been determined as 34 #+-# 1 s. Out of 104 #gamma# transitions ascribed to the "1"0"5Sn decay, 89 have been placed in the decay scheme including 52 excited states of "1"0"5In. From the EC/#beta#"+ feeding of individual states, the distribution of the Gamow-Teller (GT) strength has been derived. It is shown that the main part of the GT strength is associated with the feeding of "1"0"5In levels having excitation energies above 3 MeV. This observation can be interpreted as a sign of dominant feeding of three-quasiparticle states in "1"0"5In, which correspond to the #pi#(g_9_/_2)"-"1 #nu#d_5_/_2 shell-model configuration spread over many levels. The sum of the GT strength deduced from the present gamma ray data of B_#SIGMA#(GT)=1.46 povides a lower limit to the total GT strength. Many weak transitions, mainly from high energy levels, may not have been detected in this study and therefore part of the strength may be missed. An indirect support for this conclusion has been obtained from the analysis of the indium KX-rays intensity. This analysis indicates about 50% contribution of the electron-capture to the beta decay of "1"0"5Sn, which is interpreted as a sign of a predominant feeding of the high-energy "1"0"5In states with B_#SIGMA#(GT)#>=#3. The observed GT distribution and strength will be compared to results obtained from a finite-Fermi-system theory and a large-basis shell-model calculation. The core-polarization and higher-order hindrance factors will be discussed. (orig.)SIGLEAvailable from TIB Hannover: RO 801(94-23) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Structure of high spin states in "1"0"4Sn - E2 and E3 polarization of the "1"0"0Sn core

High spin states in "1"0"4Sn were identified in the reaction "5"8Ni("5"0Cr,2p2n) at 200 MeV and 205 MeV beam energies. The #gamma#-ray energies, intensities, multipolarities, and lifetimes of high spin states were measured with the GASP spectrometer array in combination with a plunger apparatus by means of the recoil distance Doppler shift method. The deduced level scheme and transition probabilities are compared to the results of large-scale shell model calculations using three independent two-body interactions. The agreement of the level energies is satisfactory, except for a cascade of dipole transitions at high spins. The general good agreement found for E2 transition strengths implies a large effective neutron polarization charge. The shell-model calculations do not account for the measured enhanced E3 transitions for which a core excited octupole phonon admixture is indicated. (orig.)Available from TIB Hannover: RO 801(98-18) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Proton-proton correlations in "4"0Ar+"1"9"7Au reactions and the role of the two-particle phase space

SIGLEAvailable from TIB Hannover: RO801(93-03) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Nuclear structure from N #approx =# Z to N >> Z - "1"0"0Sn, "7"8Ni, "2"0"8Pb

The single particle (hole) energies in "1"0"0Sn, as extrapolated by a shell model analysis of the neighbouring nuclei, show a remarkable similarity to those in "5"6Ni, one major shell lower. This is borne out in nearly identical I"#pi#=2"+ excitation energies, implying E(2"+)#approx =#3 MeV in "1"0"0Sn, and a large neutron effective E2 charge e#>=#1.6e. In contrast a small proton polarisation charge #delta#e#<=#0.3e is found, pointing to a large isovector charge. In "1"0"4Sn for the first time in this region strong E3 transitions with B(E3)#>=#17 Wu were identified, indicating E(3"-)#approx =#3 MeV in "1"0"0Sn. Isomer spectroscopy beyond "6"8Ni following fragmentation of a 60.3 A MeV "8"6Kr beam has provided first evidence on the neutron polarisation charge and the occupation of the #nu#g_9_/_2 orbital beyond N=40, which is at variance with shell model calculations using realistic interactions. The N=40 subshell effect seen in E(2"+) is not borne out in 2n separation energies. On the other hand the #nu#g_9_/_2-f_5_/_2 splitting of single quasiparticle energies in Ni, Fe and Cr isotopes, as deduced from M2 isomers, give no hint for deformation at Z<28, N#approx =#40. In neutron-rich nuclei around "2"0"8Pb a number of new isomers were observed in the fragmentation of a 1000 A MeV "2"3"8U beam, while 3"-excitations on high spin configurations in and adjacent to "2"0"8Pb were identified in inelastic collisions of "2"0"8Pb+"2"0"8Pb. E2 and E3 strengths from stretched configurations are compared to model expectations. (orig.)SIGLEAvailable from TIB Hannover: RO 801(98-41) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Gamow-Teller strength distribution in the beta-decay of "1"0"0Ag from total-absorption gamma spectrometry

The EC/#beta#"+-decay of the odd-odd nucleus "1"0"0Ag was studied by means of total absorption #gamma#-ray spectrometry. Most of the Gamow-Teller strength was found to be concentrated at an excitation energy of 5.6 MeV in "1"0"0Pd, the FWHM of this resonance being 1.5 MeV. The measured strength distribution which is interpreted within the BCS approximation as being due to the dominant population of four-quasiparticle excitations, resembles the distribution predicted by an advanced shell-model calculation for the "9"8Ag#->#"9"8Cd decay. (orig.)Available from TIB Hannover: RO 801(94-66) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Change of the dipole strength distributions between the neighbouring #gamma#-soft nuclei "1"9"4Pt and "1"9"6Pt

A nuclear resonance fluorescence experiment with two highly efficient EUROBALL Cluster detectors has been performed on the #gamma#-soft nucleus "1"9"4Pt. Dipole excitations were observed between 2 MeV and 4 MeV excitation energy. They are tentatively interpreted as the main fragments of the scissors mode based on the measured excitation strengths and a comparison to microscopic calculations in the framework of the quasiparticle random phase approximation (QRPA). The data indicate large differences to the neighbouring isotope "1"9"6Pt: a doubling of the observed dipole strength and a shift of the energy centroid by about 600 keV. None of the currently available models is able to reproduce these features consistently in both nuclei. (orig.)Also published in: Physics Letters B 554(2003), p. 15-20SIGLEAvailable from TIB Hannover: RN 5633(2002,28) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDeutsche Forschungsgemeinschaft (DFG), Bonn (Germany)DEGerman

Fragment flow and the multifragmentation phase space

Fragment distributions have been measured for Au + Au collisions at E/A 100 MeV and 1000 MeV. A high detection efficiency for fragments in nearly 4#pi# geometry was obtained by combining the Aladin forward spectrometer system and the MSU-Miniball/WU-Miniwall array. At both energies the maximum multiplicity of intermediate mass fragments normalized to the size of the decaying system is about one IMF per 30 nucleons but the element distributions show significant differences. Within a coalescence picture the suppression of heavy fragments in central collisions at E/A = 100 MeV may be related to a reduction of the density in momentum space which is caused by the collective expansion velocity component. (orig.)Available from TIB Hannover: RO 801(94-46) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

The nuclear liquid-gas phase transition: Present status and future perspectives

More than two decades ago, the van der Waals behavior of the nucleon -nucleon force inspired the idea of a liquid-gas phase transition in nuclear matter. Heavy-ion reactions at relativistic energies offer the unique possibility for studying this phase transition in a finite, hadronic system. A general overview of this subject is given emphasizing the most recent results on nuclear calorimetry. (orig.)Available from TIB Hannover: RO 801(96-31) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman