705 research outputs found
Large scale shell model calculations for odd-odd Mn isotopes
Large scale shell model calculations have been carried out for odd-odd
Mn isotopes in two different model spaces. First set of calculations
have been carried out in full shell valence space with two recently
derived shell interactions namely GXPF1A and KB3G treating Ca
as core. The second set of calculations have been performed in
valence space with the interaction treating Ca as core and
imposing a truncation by allowing up to a total of six particle excitations
from the 0f orbital to the upper orbitals for protons and
from the upper orbitals to the 0g orbital for neutron. For
low-lying states in Mn, the KB3G and GXPF1A both predicts good results
and for Mn, KB3G is much better than GXPF1A. For negative parity and
high-spin positive parity states in both isotopes interaction is
required. Experimental data on Mn is sparse and therefore it is not
possible to make any definite conclusions. More experimental data on negative
parity states is needed to ascertain the importance of 0g and higher
orbitals in neutron rich Mn isotopes.Comment: 5 pages, 4 figures, Submitted to Eur. Phys. J.
Z=50 shell gap near Sn from intermediate-energy Coulomb excitations in even-mass Sn isotopes
Rare isotope beams of neutron-deficient Sn nuclei from the
fragmentation of Xe were employed in an intermediate-energy Coulomb
excitation experiment yielding transition strengths.
The results indicate that these values are much larger
than predicted by current state-of-the-art shell model calculations. This
discrepancy can be explained if protons from within the Z = 50 shell are
contributing to the structure of low-energy excited states in this region. Such
contributions imply a breaking of the doubly-magic Sn core in the light
Sn isotopes.Comment: 4 pages, 4 figure
Measurement of excited states in 40Si and evidence for weakening of the N=28 shell gap
Excited states in 40Si have been established by detecting gamma-rays
coincident with inelastic scattering and nucleon removal reactions on a liquid
hydrogen target. The low excitation energy, 986(5) keV, of the 2+[1] state
provides evidence of a weakening in the N=28 shell closure in a neutron-rich
nucleus devoid of deformation-driving proton collectivity.Comment: accepted for publication in PR
Population of bound excited states in intermediate-energy fragmentation reactions
Fragmentation reactions with intermediate-energy heavy-ion beams exhibit a
wide range of reaction mechanisms, ranging from direct reactions to statistical
processes. We examine this transition by measuring the relative population of
excited states in several sd-shell nuclei produced by fragmentation with the
number of removed nucleons ranging from two to sixteen. The two-nucleon removal
is consistent with a non-dissipative process whereas the removal of more than
five nucleons appears to be mainly statistical.Comment: 5 pages, 6 figure
Spectroscopy of the odd-odd fp-shell nucleus 52Sc from secondary fragmentation
The odd-odd fp-shell nucleus 52Sc was investigated using in-beam gamma-ray
spectroscopy following secondary fragmentation of a 55V and 57Cr cocktail beam.
Aside from the known gamma-ray transition at 674(5)keV, a new decay at
E_gamma=212(3) keV was observed. It is attributed to the depopulation of a
low-lying excited level. This new state is discussed in the framework of
shell-model calculations with the GXPF1, GXPF1A, and KB3G effective
interactions. These calculations are found to be fairly robust for the
low-lying level scheme of 52Sc irrespective of the choice of the effective
interaction. In addition, the frequency of spin values predicted by the shell
model is successfully modeled by a spin distribution formulated in a
statistical approach with an empirical, energy-independent spin-cutoff
parameter.Comment: accepted for publication in PR
Enhanced collectivity in 74Ni
The neutron-rich nucleus 74Ni was studied with inverse-kinematics inelastic
proton scattering using a 74Ni radioactive beam incident on a liquid hydrogen
targetat a center-of-mass energy of 80 MeV. From the measured de-excitation
gamma-rays, the population of the first 2+ state was quantified. The
angle-integrated excitation cross section was determined to be 14(4) mb. A
deformation length of delta = 1.04(16) fm was extracted in comparison with
distorted wave theory, which suggests that the enhancement of collectivity
established for 70Ni continues up to 74Ni. A comparison with results of shell
model and quasi-particle random phase approximation calculations indicates that
the magic character of Z = 28 or N = 50 is weakened in 74Ni
Evolution of the energy spacing in odd-mass K, Cl and P isotopes for
The energy of the first excited state in the neutron-rich N=28 nucleus 45Cl
has been established via in-beam gamma-ray spectroscopy following proton
removal. This energy value completes the systematics of the
E(1/2^+_1)-E(3/2^+_1) level spacing in odd-mass K, Cl and P isotopes for
N=20-28. The results are discussed in the framework of shell-model calculations
in the sd-fp model space. The contribution of the central, spin-orbit and
tensor components is discussed from a calculation based on a proton single-hole
spectrum from G-matrix and pi + rho meson exchange potentials. A composite
model for the proton 0d_{3/2}-1s_{1/2} single-particle energy shift is
presented.Comment: Phys. Rev. C, in pres
One-neutron knockout in the vicinity of the N=32 sub-shell closure: 9Be(57Cr,56Cr+ gamma)X
The one-neutron knockout reaction 9Be(57Cr,56Cr + gamma)X has been measured
in inverse kinematics with an intermediate-energy beam. Cross sections to
individual states in 56Cr were partially untangled through the detection of the
characteristic gamma-ray transitions in coincidence with the reaction residues.
The experimental inclusive longitudinal momentum distribution and the yields to
individual states are compared to calculations that combine spectroscopic
factors from the full fp shell model and nucleon-removal cross sections
computed in a few-body eikonal approach.Comment: PRC, in pres
Variation with mass of \boldmath{B(E3; 0_1^+ \to 3_1^-)} transition rates in even-mass xenon nuclei
transition matrix elements have been measured for
even-mass Xe nuclei using sub-barrier Coulomb excitation in inverse
kinematics. The trends in energy and
excitation strengths are well reproduced using phenomenological models based on
a strong coupling picture with a soft quadrupole mode and an increasing
occupation of the intruder orbital.Comment: 5 pages, 4 figures, PRC in pres
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