Monday, March 11, 2002 - DPG-Tagungen

Nuclear Physics Monday
=38±4 ms)to 56 Ni [1], (ii) the accurate determination of the branching
ratio for the 58 Cu(1 + )→ 58 Ni(0 + ) β transition (81.2±0.5 %), which serves
as a calibration in deducing the Gamow-Teller strength distribution from
high-resolution 58 Ni( 3 He,t) 58 Cu data [2], and (iii) an attempt to reach a
precision of 4 parts in 10 4 for the half-life of the superallowed 0 + →0 + βdecay
of 62 Ga by accumulating about 2×10 6 positron events. Finally, an
outlook will be given, including in particular the novel technique of extracting
short-lived tin isotopes as singly charged sulfide molecules from
the ion source, which opens exciting perspectives for future β-decay experiments
on 102 Sn and 100 Sn.
[1] A. Jokinen et al., submitted to Eur. Phys. J. A.
[2] Z. Janas et al., Eur. Phys. J. A 12, 143 (2001).
Group Report HK 3.3 Mon 17:15 B
Investigation of the level scheme of 144 Gd and lifetimes of the
triaxial quadrupole band — •R.M. Lieder 1 , W. Gast 1 , H.M.
Jäger 1 , L. Mihailescu 1 , A.A. Pasternak 2 , E.O. Podsvirova 2 , D.
Bazzacco 3 , R. Menegazzo 3 , S. Lunardi 3 , C. Rossi Alvarez 3 , G.
de Angelis 4 , E. Farnea 4 , A. Gadea 4 , D.R. Napoli 4 , T. Rza¸ca-
Urban 5 , W. Urban 5 ,andA. Dewald 6 — 1 IKP, FZ Jülich, D-52425
Jülich — 2 A.F. Joffe PTI, RU-194021 St. Petersburg — 3 INFN, Sezione
di Padova, I-35131 Padova — 4 INFN, LNL, I-35020 Legnaro — 5 IEP,
Univ. Warsaw, PL-00-681 Warsaw — 6 IKP, Univ. Köln, D-50937 Köln
High-spin states in 144 Gd have been excited in the 100 Mo( 48 Ti,4n) reaction
at 215 MeV and studied with EUROBALL at the LNL, Italy.
Several dipole and stretched E2 cascades have been observed. The study
of lifetimes of the E2 cascades is of importance for the understanding of
the transition from highly to superdeformed states between the A ≈ 130
and A ≈ 150 regions. This transition is expected to occur via triaxial
shapes. The strongest E2 cascade in 144 Gd is considered to have a
configuration involving rotation aligned h11/2 protons as well as rotation
aligned h11/2 neutron holes and h9/2 neutrons resulting in a well
deformed triaxial nuclear shape. More information on the configuration
of this band was obtained in a DSA study with GASP at the LNL, Italy
using the 114 Cd( 36 S,6n) reaction at E = 182 MeV. The target consisted of
a 1.2 mg/cm 2 114 Cd foil backed by a 1.2 mg/cm 2 Ta and a 55 mg/cm 2 Bi
layer. Because most of the γ-lines of interest are contaminated by background
lines special techniques have been developed for the analysis. The
results of the lifetime analysis support the proposed interpretation.
HK 3.4 Mon 17:45 B
New methods for measuring nuclear skins — •A. Krasznahorkay
1,2 , H. Akimune 3 , A.M. van den Berg 2 , N. Blasi 4 , S.
Brandenburg 2 , M. Csatlós 1 , H. Fujimura 3 , M. Fujiwara 3,5 , J.
Gulyás 1 , M. Hagemann 6 , K. Hara 3 , M. N. Harakeh 2 , M. Hunyadi
2 , M. de Huu 2 , F. Ihara 3 , T. Ishikawa 7 , Z. Máté 1 , D. Sohler 1 ,
S.Y. van der Werf 2 ,andL. Zolnai 1 — 1 ATOMKI, Debrecen, Hungary
— 2 KVI, Groningen, The Netherlands — 3 RCNP, Osaka, Japan —
4 INFN, Milano, Italy — 5 JAERI, Tokai, Japan — 6 Univ. Gent, Belgium
— 7 Univ. Kyoto, Japan
The neutron-skin thickness of 208 Pb and 114,124 Sn has been investigated
in order to constrain the symmetry energy term of the nuclear
energy functional. The precise knowledge of the symmetry energy is essential
not only for describing the structure of neutron-rich nuclei, but
also for describing the properties of the neutron-rich matter in nuclear
astrophysics. We have used inelastic alpha scattering to excite the giant
dipole resonance (GDR). The cross section of this process depends
strongly on ∆Rnp/R, the radial difference of the neutron and proton
densities [1]. We have also used the excitation of the spin-dipole resonance
(SDR) to measure the neutron-skin thickness since the total L=1
strength of the SDR is sensitive to it [2]. Recently new experiments were
carried out at the KVI using 196 MeV α and 177 MeV 3 He beams from
the AGOR superconducting cyclotron. A critical test of both the GDR
and SDR methods will be discussed.
[1] A. Krasznahorkay et al., Phys. Rev. Lett. 66, 1287 (1991)
[2] A. Krasznahorkay et al., Phys. Rev. Lett. 82, 3216 (1999).
HK 3.5 Mon 18:00 B
Nuclear matter distribution of light neutron rich He nuclei from
elastic proton scattering at large momentum transfer — •Oleg
Kisselev for the S174 collaboration — Gesellschaft für Schwerionenforschung
mbH, Planckstrasse 1, D-64291 Darmstadt
Elastic proton scattering from the 6 He and 8 He halo nuclei was investigated
in inverse kinematics at energies around 700 MeV/u at GSI Darmstadt.
The experimental setup consisted of a liquid hydrogen target, a
forward spectrometer for tracking and identifying the projectile nuclei,
and a tracking system for the detection of the recoil protons. This setup
allowed for a high precision and low background measurement. The aim
of the experiment was to deduce the differential p 6 He and p 8 He cross sections
for the region of high momentum transfer close to the expected first
diffraction minimum. This new information together with the data obtained
at small momentum transfer provides additional knowledge about
the structure of the alpha-like core in 6 He and 8 He. The present status
of the data analysis and first results will be presented.
HK 3.6 Mon 18:15 B
Alpha decay of 114 Ba — •C. Mazzocchi for the GSI-ISOL collaboration
— GSI, Darmstadt, Germany
Alpha decay is a rich source of nuclear-structure information, offering
insight into properties such as ground-state binding energies and spectroscopic
factors for α-particle emission, in particular for neutron-deficient
isotopes beyond the doubly-magic nucleus 100 Sn. Based on this motiva-
tion we searched for the α decay of 114 Ba (T1/2 = 430 +300
−150 ms [1]). The
114 Ba nuclei were produced through the 58 Ni( 58 Ni,2n) reaction, separated
from other reaction products as a mass-separated and chemically clean
beam of 114 Ba 19 F + ions by means of the ISOL facility of GSI Darmstadt,
implanted into a stopper foil, and studied by using silicon-detector telescopes
for decay spectroscopy.
We measured for the first time the α-particle energy (3410±40 keV)
of 114 Ba, the half-life (160 +290
−60 ms) of its daughter nucleus 110 Xe, and the
α-branching ratios and widths for these two isotopes and for the granddaughter
nucleus 106 Te [2]. The increase of the α-particle energies along
the α-decay chain from 114 Ba to 102 Sn is a clear signature of the double
shell-closure occurring at 100 Sn. The experimental values obtained for
the α-decay Q values of these three isotopes as well as for the Q value
for 12 C emission from 114 Ba (19000±40 keV) will be dicussed in comparison
with theoretical predictions. In view of the large uncertainties of
the reduced α-widths, no firm conclusions can be drawn concerning the
occurrence of superallowed α decay.
[1] Z. Janas et al., Nucl. Phys. A 627, 119 (1997).
[2] C. Mazzocchi et al., submitted to Phys. Lett. B.
HK 3.7 Mon 18:30 B
Simple Parametrization of neutron separation energies in terms
of the neutron to proton ratio N/Z ∗ — •K. Vogt, T. Hartmann,
and A. Zilges — Institut für Kernphysik, Technische Universität Darmstadt,
D-64289 Darmstadt, Germany
It is shown that single- and two-nucleon separation energies can be
parametrized in a new way using the neutron to proton ratio N/Z and
the mass number A. Very simple empirical formulas have been achieved
using a least squares fit to all available experimental data [1]. It is demonstrated
that the observed N/Z dependence can be derived from the Fermi
Gas model. For an estimate of the usefulness of these formulas, the resulting
neutron separation energies are compared to results from several
mass formulas currently in use [2,3]. As an outlook, possible practical
applications are discussed.
∗ supported by the DFG (contract Zi 510/2-1 and FOR 272/2-1).
[1]K.Vogt,T.Hartmann,A.Zilges,Phys.Lett.B517 (2001)
[2] P. Möller, J. R. Nix, W. D. Myers, and W. J. Swiatecki, At. Data
Nucl. Data Tables, 59, 185 (1995)
[3] F.Tondeur,S.Goriely,J.M.Pearson,andM.Onsi,Phys. Rev. C
62, 024308 (2000)
HK 3.8 Mon 18:45 B
Calculated groundstate properties of Er-isotopes in comparison
with messured 2 + -states — •Thomas Cornelius 1 , M. Bender 2 ,
T. Bürvenich 1 , A. Sulaksono 1 , P. Fleischer 3 , S . S chramm 4 ,
J. A. Maruhn 1 , P.–G. Reinhard 3 , J. H. Hamilton 5 , and W.
Greiner 1 — 1 Institut für Theoretische Physik, Universität Frankfurt am
Main — 2 Service de Physique Nucléaire Théorique, Université Librede
Bruxelles — 3 Institut für Theoretische Physik II, Universität Erlangen-
Nürnberg — 4 Nuclear Theory Group, Argonne National Laboratory —
5 Department of Physics, Vanderbilt University, Nashville
Self-consistent mean-field models are nowadays well developed and provide
a pertinent picture of nuclear properties throughout the whole mass
table. We consider two different models, the Skyrme-Hartree-Fock approach
(SHF) and the relativistic mean-field model (RMF). In our former
investigations deformed calculations appear to be important for some observables
like the 2-proton-shell-gap [1].
In our talk we want to show a possible correlation of the lowest, exper-