424 research outputs found
High-spin states with seniority v=4,4,6 in 119-126Sn
The 119-126Sn nuclei have been produced as fission fragments in two reactions
induced by heavy ions: 12C+238U at 90 MeV bombarding energy, 18O+208Pb at 85
MeV. Their level schemes have been built from gamma rays detected using the
Euroball array. High-spin states located above the long-lived isomeric states
of the even- and odd-A 120-126Sn nuclei have been identified. Moreover isomeric
states lying around 4.5 MeV have been established in 120,122,124,126Sn from the
delayed coincidences between the fission fragment detector SAPhIR and the
Euroball array. The states located above 3-MeV excitation energy are ascribed
to several broken pairs of neutrons occupying the nu h11/2 orbit. The maximum
value of angular momentum available in such a high-j shell, i.e. for
mid-occupation and the breaking of the three neutron pairs, has been
identified. This process is observed for the first time in spherical nuclei.Comment: 20 pages, 22 figures, 12 tables, accepted for publication in Physical
Review
Charge-radius change and nuclear moments in the heavy tin isotopes from laser spectroscopy: Charge radius of Sn
NESTER ACCLaser spectroscopy measurements have been carried out on the neutron-rich tin isotopes with the COMPLIS experimental setup. Using the optical transition, hyperfine spectra of Sn and were recorded for the first time. The nuclear moments and the mean square charge radius variation (\delta, the absolute charge radii of these isotopes were deduced in particular that of the doubly magic Sn nucleus. The comparison of the results with several mean-field-type calculations have shown that dynamical effects play an important role in the tin isotopes
High-spin structures of five N=82 isotones: 136Xe, 137Cs, 138Ba, 139La, and 140Ce
Five N=82 isotones have been produced in two fusion-fission reactions and
their gamma-rays studied with the Euroball array. The high-spin states of 139La
have been identified for the first time, while the high-spin yrast and
near-to-yrast structures of the four others have been greatly extended. From
angular correlation analysis,spin values have been assigned to some states of
136Xe and 137Cs. Several cascades involving gamma-rays of 139La have been found
to be delayed, they deexcite an isomeric state with T1/2= 315(35) ns located at
1800-keV excitation energy. The excited states of these five N=82 isotones are
expected to be due to various proton excitations involving the three high-j
subshells located above the Z=50 shell closure. This is confirmed by the
results of shell-model calculations performed in this work. In addition,
high-spin states corresponding to the excitation of the neutron core have been
unambiguously identified in 136Xe, 137Cs, and 138Ba.Comment: 18 pages, 18 figures, 10 tables, accepted for publication in Phys.
Rev.
Is there a dark decay of neutrons in He ?
Motivated by the four standard deviations discrepancy between the mean values
for the neutron lifetime obtained from beam and bottle experiments, we have
searched for a hypothetical neutron dark decay in He nuclei through the
channel . The experiment used a
25~keV high intensity He beam with a high efficiency neutron detector.
The search for a signal correlated with the He activity in the neutron
detection rate resulted in a branching ratio with a 95\% C.L. over the mass window MeV. This result is five orders of magnitude smaller than required
to solve the neutron lifetime discrepancy
Release properties of UC and molten U targets
The release properties of UC and molten U thick targets associated with a Nier- Bernas ion source have been studied. Two experimental methods are used to extract the release time. Results are presented and discussed for Kr, Cd, I and Xe
Recent results on neutron rich tin isotopes by laser spectroscopy
Laser spectroscopy measurements have been performed on neutron rich tin isotopes using the COMPLIS experimental setup. The nuclear charge radii of the even-even isotopes from A=108 to 132 are compared to the results of macroscopic and microscopic calculations. The improvements and optimizations needed to perform the isotope shift measurement on Sn are presented
Intruder negative-parity states of neutron-rich Si33
Yrast states in the neutron-rich 1433Si19 nucleus have been studied using binary grazing reactions produced by the interaction of a 215-MeV beam of S36 ions with a thin Pb208 target. An experimental setup that combines the large-acceptance magnetic spectrometer PRISMA and the high-efficiency γ-ray detection array CLARA was used in the experiment. Four new γ-ray photopeaks at energies of 971, 1724, 1772, and 2655 keV were observed and assigned to the Si33 level scheme. The experimental level scheme is compared with the results of 1ω p-sd-pf large-scale shell-model calculations using the recently developed PSDPFB effective interaction; good agreement is obtained. The structure of the populated states of Si33 is discussed within the context of an odd neutron coupled to states of the Si32 core. © 2010 The American Physical Society.This work was supported in part by the EPSRC (UK) and by the European Union under Contract No. RII3-CT-2004-506065. Five of us (D.O., M.B., A.H., K.K., and A.P.)acknowledge financial support from the EPSRC. Z.M.W acknowledges support from ORSAS and from the University of the West of Scotland. A.J. acknowledges financial supportfrom the Spanish Ministerio de Ciencia e Innovación under Contract Nos. FPA2007-66069 and FPA2009-13377-C02-02. Zs.D. acknowledges the financial support from OTKA Project No. K68801.Peer Reviewe
COMPLIS experiments : COllaboration for spectroscopy Measurements using a Pulsed Laser Ion Source
Laser spectroscopy measurements have been carried out on very neutron-deficient isotopes of Au, Pt and Ir, produced as daughter elements from a Hg ISOLDE beam. For these transitional region nuclides, the hyperfine structure (HFS) and isotope shift (IS) were measured by Resonance Ionization Spectroscopy (RIS). Magnetic moments μ, spectroscopic quadrupole moments Qs and changes of the nuclear mean square charge radius δ〈rc 2〉along isotopic series have been extracted. For some results, a detailed comparison with theoretical predictions is presented. (Springer
First in-beam γ -ray study of the level structure of neutron-rich S 39
International audienceThe neutron-rich S39 nucleus has been studied using binary grazing reactions produced by the interaction of a 215-MeV beam of S36 ions with a thin Pb208 target. The magnetic spectrometer, PRISMA, and the γ-ray array, CLARA, were used in the measurements. Gamma-ray transitions of the following energies were observed: 339, 398, 466, 705, 1517, 1656, and 1724 keV. Five of the observed transitions have been tentatively assigned to the decay of excited states with spins up to (11/2−). The results of a state-of-the-art shell-model calculation of the level scheme of S39 using the SDPF-U effective interaction are also presented. The systematic behavior of the excitation energy of the first 11/2− states in the odd-A isotopes of sulfur and argon is discussed in relation to the excitation energy of the first excited 2+ states of the adjacent even-A isotopes. The states of S39 that have the components in their wave functions corresponding to three neutrons in the 1f7/2 orbital outside the N=20 core have also been discussed within the context of the 0 ℏω shell-model calculations presented here
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