624 research outputs found
Very high rotational frequencies and band termination in 73Br
Rotational bands in 73Br have been investigated up to spins of 65/2 using the
EUROBALL III spectrometer. One of the negative-parity bands displays the
highest rotational frequency 1.85 MeV reported to date in nuclei with mass
number greater than 25. At high frequencies, the experimental dynamic moment of
inertia for all bands decrease to very low values, indicating a loss of
collectivity. The bands are described in the configuration-dependent cranked
Nilsson-Strutinsky model. The calculations indicate that one of the
negative-parity bands is observed up to its terminating single-particle state
at spin 63/2. This result establishes the first band termination case in the A
= 70 mass region.Comment: 6 pages, 6 figures, submitted to Phys. Rev. C as a Rapid
Communicatio
A one-dimensional lattice model for a quantum mechanical free particle
Two types of particles, A and B with their corresponding antiparticles, are
defined in a one dimensional cyclic lattice with an odd number of sites. In
each step of time evolution, each particle acts as a source for the
polarization field of the other type of particle with nonlocal action but with
an effect decreasing with the distance: A -->...\bar{B} B \bar{B} B \bar{B} ...
; B --> A \bar{A} A \bar{A} A ... . It is shown that the combined distribution
of these particles obeys the time evolution of a free particle as given by
quantum mechanics.Comment: 8 pages. Revte
Level structure of 69Se
15 págs.; 9 figs.; 5 tabs. ; PACS number(s): 23.20.Lv, 21.10.Re, 27.50.1e, 21.60.2nExcited levels in 69Se have been studied using the 40Ca(32S,2pn)69Se reaction at 95- and 105-MeV beam energy, γ rays have been detected with the EUROBALL spectrometer operated in conjunction with the neutron wall and the charged-particle detector array EUCLIDES. New level sequences with positive and negative parities have been identified from n-γγ and n-γγγ coincidences. Spins have been assigned to many of the levels on the basis of angular distribution and directional correlation measurements. Excitation energies of the positive-parity yrast band and the branching ratios of its decay are compared with the predictions of the rigid triaxial rotor plus particle model. ©2004 The American Physical SocietyA. J. acknowledges financial support from the Deutsche Forschungsgemeinshaft (DPG)
within the Heisenberg program. This work was supported
by BMBF under Contract Nos. 06 OK 958 and 06 GÖ 951
and the EUROVIV Contract No. HPRI-CT-1999-000783.Peer Reviewe
Coulomb excitation of 73Ga
The B(E2; Ii -> If) values for transitions in 71Ga and 73Ga were deduced from
a Coulomb excitation experiment at the safe energy of 2.95 MeV/nucleon using
post-accelerated beams of 71,73Ga at the REX-ISOLDE on-line isotope mass
separator facility. The emitted gamma rays were detected by the
MINIBALL-detector array and B(E2; Ii->If) values were obtained from the yields
normalized to the known strength of the 2+ -> 0+ transition in the 120Sn
target. The comparison of these new results with the data of less neutron-rich
gallium isotopes shows a shift of the E2 collectivity towards lower excitation
energy when adding neutrons beyond N = 40. This supports conclusions from
previous studies of the gallium isotopes which indicated a structural change in
this isotopical chain between N = 40 and N = 42. Combined with recent
measurements from collinear laser spectroscopy showing a 1/2- spin and parity
for the ground state, the extracted results revealed evidence for a 1/2-; 3/2-
doublet near the ground state in 73 31Ga42 differing by at most 0.8 keV in
energy
Coulomb excitation of Ni at safe energies
The value in Ni has been measured using Coulomb
excitation at safe energies. The Ni radioactive beam was
post-accelerated at the ISOLDE facility (CERN) to 2.9 MeV/u. The emitted
rays were detected by the MINIBALL detector array. A kinematic
particle reconstruction was performed in order to increase the measured c.m.
angular range of the excitation cross section. The obtained value of
2.8 10 efm is in good agreement with the value
measured at intermediate energy Coulomb excitation, confirming the low
transition probability.Comment: 4 pages, 5 figure
First Results on In-Beam gamma Spectroscopy of Neutron-Rich Na and Mg Isotopes at REX-ISOLDE
After the successful commissioning of the radioactive beam experiment at
ISOLDE (REX-ISOLDE) - an accelerator for exotic nuclei produced by ISOLDE -
first physics experiments using these beams were performed. Initial experiments
focused on the region of deformation in the vicinity of the neutron-rich Na and
Mg isotopes. Preliminary results show the high potential and physics
opportunities offered by the exotic isotope accelerator REX in conjunction with
the modern Germanium gamma spectrometer MINIBALL.Comment: 7 pages, RNB6 conference contributio
Response of AGATA Segmented HPGe Detectors to Gamma Rays up to 15.1 MeV
The response of AGATA segmented HPGe detectors to gamma rays in the energy
range 2-15 MeV was measured. The 15.1 MeV gamma rays were produced using the
reaction d(11B,ng)12C at Ebeam = 19.1 MeV, while gamma-rays between 2 to 9 MeV
were produced using an Am-Be-Fe radioactive source. The energy resolution and
linearity were studied and the energy-to-pulse-height conversion resulted to be
linear within 0.05%. Experimental interaction multiplicity distributions are
discussed and compared with the results of Geant4 simulations. It is shown that
the application of gamma-ray tracking allows a suppression of background
radiation following neutron capture by Ge nuclei. Finally the Doppler
correction for the 15.1 MeV gamma line, performed using the position
information extracted with Pulse-shape Analysis, is discussed.Comment: 10 pages, 11 figure
Experimental evidence for 56Ni-core breaking from the low-spin structure of the N=Z nucleus 58Cu
Low-spin states in the odd-odd N=Z nucleus 58Cu were investigated with the
58Ni(p,n gamma)58Cu fusion evaporation reaction at the FN-tandem accelerator in
Cologne. Seventeen low spin states below 3.6 MeV and 17 new transitions were
observed. Ten multipole mixing ratios and 17 gamma-branching ratios were
determined for the first time. New detailed spectroscopic information on the
2+,2 state, the Isobaric Analogue State (IAS) of the 2+,1,T=1 state of 58Ni,
makes 58Cu the heaviest odd-odd N=Z nucleus with known B(E2;2+,T=1 --> 0+,T=1)
value. The 4^+ state at 2.751 MeV, observed here for the first time, is
identified as the IAS of the 4+,1,T=1 state in 58Ni. The new data are compared
to full pf-shell model calculations with the novel GXPF1 residual interaction
and to calculations within a pf5/2 configurational space with a residual
surface delta interaction. The role of the 56Ni core excitations for the
low-spin structure in 58Cu is discussed.Comment: 15 pages, 7 figures, submitted to Phys. Rev.
A New 76Ge Double Beta Decay Experiment at LNGS
This Letter of Intent has been submitted to the Scientific Committee of the
INFN Laboratori Nazionali del Gran Sasso (LNGS) in March 2004. It describes a
novel facility at the LNGS to study the double beta decay of 76Ge using an
(optionally active) cryogenic fluid shield. The setup will allow to scrutinize
with high significance on a short time scale the current evidence for
neutrinoless double beta decay of 76Ge using the existing 76Ge diodes from the
previous Heidelberg-Moscow and IGEX experiments. An increase in the lifetime
limit can be achieved by adding more enriched detectors, remaining thereby
background-free up to a few 100 kg-years of exposure.Comment: 67 pages, 19 eps figures, 17 tables, gzipped tar fil
- …