D. Henzlova

Neutron-proton asymmetry dependence of spectroscopic factors in Ar isotopes

Spectroscopic factors have been extracted for proton-rich 34Ar and neutron-rich 46Ar using the (p, d) neutron transfer reaction. The experimental results show little reduction of the ground state neutron spectroscopic factor of the proton-rich nucleus 34Ar compared to that of 46Ar. The results suggest that correlations, which generally reduce such spectroscopic factors, do not depend strongly on the neutron-proton asymmetry of the nucleus in this isotopic region as was reported in knockout reactions. The present results are consistent with results from systematic studies of transfer reactions but inconsistent with the trends observed in knockout reaction measurements.

Production of medium-mass neutron-rich nuclei in reactions induced by Xe 136 projectiles at 1 A GeV on a beryllium target

Production cross sections of medium-mass neutron-rich nuclei obtained in the fragmentation of {sup 136}Xe projectiles at 1 A GeV have been measured with the FRagment Separator (FRS) at GSI. The measured cross sections are compared to {sup 238}U fission yields and model calculations to determine the optimum reaction mechanism to extend the limits of the chart of the nuclides around the r-process waiting point at N=82.

Experimental investigation of the residues produced in the 136Xe + Pb and 124Xe + Pb fragmentation reactions at 1A GeV

The nuclide cross sections and longitudinal velocity distributions of residues produced in the reactions of {sup 136}Xe and {sup 124}Xe at 1A GeV in a lead target were measured at the high-resolution magnetic spectrometer, the fragment separator (FRS) of GSI. The data cover a broad range of isotopes of the elements between Z=3 and Z=56 for {sup 136}Xe and between Z=5 and Z=55 for {sup 124}Xe, reaching down to cross sections of a few microbarns. The velocity distributions exhibit a Gaussian shape for masses above A=20, while more complex behavior is observed for lighter masses. The isotopic distributions for both reactions preserve a memory on the projectile N/Z ratio over the whole residue mass range.

Mechanisms in Knockout Reactions

We report the first detailed study of the relative importance of the stripping and diffraction mechanisms involved in nucleon knockout reactions, by the use of a coincidence measurement of the residue and fast proton following one-proton knockout reactions. The measurements used the S800 spectrograph in combination with the HiRA detector array at the NSCL. Results for the reactions 9Be(9C,8B+X)Y and 9Be(8B,7Be+X)Y are presented and compared with theoretical predictions for the two reaction mechanisms calculated using the eikonal model. The data show a clear distinction between the stripping and diffraction mechanisms and the measured relative proportions are very well reproduced by the reaction theory. This agreement adds support to the results of knockout reaction analyses and their applications to the spectroscopy of rare isotopes.

N/Z DEPENDENCE OF PROJECTILE FRAGMENTATION

The N/Z dependence of projectile fragmentation at relativistic energies has been studied in a recent experiment at the GSI laboratory with the ALADiN forward spectrometer coupled to the LAND neutron detector. Besides a primary beam of 124Sn, also secondary beams of 124La and 107Sn delivered by the FRS fragment separator have been used in order to extend the range of isotopic compositions of the produced spectator sources. With the achieved mass resolution of ΔA/A ≈ 1.5%, lighter isotopes with atomic numbers Z ≤ 10 are individually resolved. The presently ongoing analyses of the measured isotope yields focus on isoscaling and its relation to the properties of hot fragments at freeze-out and on the derivation of chemical freeze-out temperatures which are found to be independent of the isotopic composition of the studied systems. The latter result is at variance with the predictions for limiting temperatures as obtained with finite-temperature Hartree-Fock calculations.

Discriminant analysis and secondary-beam charge recognition

The discriminant-analysis method has been applied to optimize the exotic-beam charge recognition in a projectile fragmentation experiment. The experiment was carried out at the GSI using the fragment separator (FRS) to produce and select the relativistic secondary beams, and the ALADIN setup to measure their fragmentation products following collisions with Sn target nuclei. The beams of neutron poor isotopes around La-124 and Sn-107 were selected to study the isospin dependence of the limiting temperature of heavy nuclei by comparing with results for stable Sn-124 projectiles. A dedicated detector to measure the projectile charge upstream of the reaction target was not used, and alternative methods had to be developed. The presented method, based on the multivariate discriminant analysis, allowed to increase the efficacy of charge recognition up to about 90%, which was about 20% more than achieved with the simple scalar methods.

Extrapolation of neutron-rich isotope cross-sections from projectile fragmentation

Using the measured fragmentation cross-sections produced from the 48 Ca and 64 Ni beams at 140 MeV per nucleon on 9 Be and 181 Ta targets, we find that the cross-sections of unmeasured neutron-rich nuclei can be extrapolated using a systematic trend involving the average binding energy. The extrapolated cross-sections will be very useful in planning experiments with neutron-rich isotopes produced from projectile fragmentation. The proposed method is general and could be applied to other fragmentation systems including those used in other radioactive ion beam facilities. Copyright c EPLA, 2007

Neutron spectroscopic factors of 55Ni hole-states from (p,d) transfer reactions

Abstract Spectroscopic information has been extracted on the hole-states of 55Ni, the least known of the quartet of nuclei (55Ni, 57Ni, 55Co and 57Cu), one nucleon away from 56Ni, the N = Z = 28 double magic nucleus. Using the H 1 ( Ni 56 , d ) Ni 55 transfer reaction in inverse kinematics, neutron spectroscopic factors, spins and parities have been extracted for the f 7 / 2 , p 3 / 2 and the s 1 / 2 hole-states of 55Ni. These new data provide a benchmark for large basis calculations that include nucleonic orbits in both the sd and pf shells. State of the art calculations have been performed to describe the excitation energies and spectroscopic factors of the s 1 / 2 hole-state below Fermi energy.

Angular dependence in proton-proton correlation functions in central 40Ca+40Ca and 48Ca+48Ca reactions

The angular dependence of proton-proton correlation functions is studied in central

Isotopic dependence of the caloric curve

^{40}Ca+^{40}Ca