104 research outputs found
Lifetime determination of excited states in Cd-106
Two separate experiments using the Differential Decay Curve Method have been performed to extract mean lifetimes of excited states in 106 Cd. The inedium-spin states of interest were populated by the Mo-98(C-12, 4n) Cd-106 reaction performed at the Wright Nuclear Structure Lab., Yale University. From this experiment, two isomeric state mean lifetimes have been deduced. The low-lying states were populated by the Mo-96(C-13, 3n)Cd-106 reaction performed at the Institut fur Kernphysik, Universitat zu Koln. The mean lifetime of the I-pi = 2(1)(+) state was deduced, tentatively, as 16.4(9) ps. This value differs from the previously accepted literature value from Coulomb excitation of 10.43(9) ps
Vibrational and rotational sequences in 101 Mo and 103,4 Ru studied via multinucleon transfer reactions
The near yrast states of 101 Mo and 103,104 Ru have been studied following their population via heavy ion multinucleon transfer reactions between a 136 Xe beam and a thin, self supporting 100 Mo target. The ground state sequence in 104 Ru can be understood as demonstrating a simple evolution from a quasi vibrational structure at lower spins to statically deformed, quasi rotational excitation involving the population of a pair of low Omega h11 2 neutron orbitals. The effect of the decoupled h11 2 orbital on this vibration to rotational evolution is demonstrated by an extension of the E GOS prescription to include odd A nuclei. The experimental results are also compared with self consistent Total Routhian Surface calculations which also highlight the polarising role of the highly aligned neutron h11 2 orbital in these nucle
Core-coupled states and split proton-neutron quasi-particle multiplets in 122-126Ag
Neutron-rich silver isotopes were populated in the fragmentation of a 136Xe
beam and the relativistic fission of 238U. The fragments were mass analyzed
with the GSI Fragment separator and subsequently implanted into a passive
stopper. Isomeric transitions were detected by 105 HPGe detectors. Eight
isomeric states were observed in 122-126Ag nuclei. The level schemes of
122,123,125Ag were revised and extended with isomeric transitions being
observed for the first time. The excited states in the odd-mass silver isotopes
are interpreted as core-coupled states. The isomeric states in the even-mass
silver isotopes are discussed in the framework of the proton-neutron split
multiplets. The results of shell-model calculations, performed for the most
neutron-rich silver nuclei are compared to the experimental data
Evidence for octupole collectivity in Pt-172
Excited states in the extremely neutron-deficient nucleus Pt-172 were populated via Ru-96(Kr-78, 2p) and Mo-92(Kr-83, 3n) reactions. The level scheme has been extended up to an excitation energy of approximate to 5MeV and tentative spin-parity assignments up to I-pi = 18(+). Linear polarization and angular distribution measurements were used to determine the electromagnetic E1 character of the dipole transitions connecting the positive-parity ground-state band with an excited side-band, firmly establishing it as a negativeparity band. The lowestmember of this negative-parity structure was firmly assigned spin-parity 3(-). In addition, we observed an E3 transition from this 3(-) state to the ground state, providing direct evidence for octupole collectivity in Pt-172. Large-scale shell model (LSSM) and total Routhian surface (TRS) calculations have been performed, supporting the interpretation of the 3(-) state as a collective octupole-vibrational state.Peer reviewe
Evidence for a spin-aligned neutron-proton paired phase from the level structure of Pd
The general phenomenon of shell structure in atomic nuclei has been
understood since the pioneering work of Goeppert-Mayer, Haxel, Jensen and
Suess.They realized that the experimental evidence for nuclear magic numbers
could be explained by introducing a strong spin-orbit interaction in the
nuclear shell model potential. However, our detailed knowledge of nuclear
forces and the mechanisms governing the structure of nuclei, in particular far
from stability, is still incomplete. In nuclei with equal neutron and proton
numbers (), the unique nature of the atomic nucleus as an object
composed of two distinct types of fermions can be expressed as enhanced
correlations arising between neutrons and protons occupying orbitals with the
same quantum numbers. Such correlations have been predicted to favor a new type
of nuclear superfluidity; isoscalar neutron-proton pairing, in addition to
normal isovector pairing (see Fig. 1). Despite many experimental efforts these
predictions have not been confirmed. Here, we report on the first observation
of excited states in nucleus Pd. Gamma rays emitted
following the Ni(Ar,2)Pd fusion-evaporation reaction
were identified using a combination of state-of-the-art high-resolution
{\gamma}-ray, charged-particle and neutron detector systems. Our results reveal
evidence for a spin-aligned, isoscalar neutron-proton coupling scheme,
different from the previous prediction. We suggest that this coupling scheme
replaces normal superfluidity (characterized by seniority coupling) in the
ground and low-lying excited states of the heaviest N = Z nuclei. The strong
isoscalar neutron- proton correlations in these nuclei are predicted to
have a considerable impact on their level structures, and to influence the
dynamics of the stellar rapid proton capture nucleosynthesis process.Comment: 13 pages, 3 figure
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