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A Kirwan

Bio: A Kirwan is an academic researcher from University College West. The author has contributed to research in topics: Recoil & Yrast. The author has an hindex of 7, co-authored 8 publications receiving 109 citations.

Papers
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Journal ArticleDOI
TL;DR: In this article, excited states in the odd-odd nuclei 128,130La have been investigated to high spin using gamma-ray spectroscopy, and two distinct bands are seen, one based on a pi h11/2(X) nu h 11/2/2 structure and the other based on pi h 11 /2/X/nu g7/2 configuration.
Abstract: Excited states in the odd-odd nuclei 128,130La have been investigated to high spin using gamma -ray spectroscopy. Two distinct bands are seen, one based on a pi h11/2(X) nu h11/2 structure and the other on a pi h11/2(X) nu g7/2 configuration. Backbends are observed in both configurations for both nuclei and the nature of the particles responsible can be conclusively proved. Experimental variation in the energy-level signature splitting and B(M1)/B(E2) ratios are discussed in terms of the polarising effects of the odd proton and odd neutron on the soft collective core. The results are discussed in terms of the cranked shell model, odd-odd particle-rotor calculations and total Routhian surface calculations. They are also compared to neighbouring odd and odd-odd systems.

23 citations

Journal ArticleDOI
TL;DR: The experimental evidence for these bands is discussed in terms of the variation in energy-level signature splitting, B(M1)/B(E2) ratios and mixing ratios as a function of rotational frequency and single-particle configuration as mentioned in this paper.
Abstract: Excited states in the nuclei 128,130La have been investigated to high spin using gamma -ray spectroscopy techniques. In addition to the main rotational structures based on a prolate collective rotor, and a superdeformed band in 130La, two bands are seen with properties similar to the collective oblate structure proposed for 131La. The experimental evidence for these bands is discussed in terms of the variation in energy-level signature splitting, B(M1)/B(E2) ratios and mixing ratios as a function of rotational frequency and single-particle configuration. These results are interpreted using odd-odd particle-rotor model calculations and self-consistent cranking calculations. They are compared with the proposed 'collective oblate' bands in other nuclei in the A=130 region and possible evidence for collective oblate shape co-existence is presented.

20 citations

Journal ArticleDOI
TL;DR: In this paper, a mean lifetime measurement has been carried out on the states in the superdeformed band found in 131Ce using the Doppler shift attenuation method (DSAM).
Abstract: A mean lifetime measurement has been carried out on the states in the superdeformed band found in 131Ce using the Doppler shift attenuation method (DSAM). The measured intrinsic nuclear quadrupole moment is Q0 approximately=6 eb, assuming constant deformation, which corresponds to a quadrupole deformation beta 2 approximately=0.35. This is considerably smaller than the value deduced for 132Ce.

17 citations

Journal ArticleDOI
TL;DR: In this paper, the negative-parity sidebands in the yrast and negative parity sideband in both nuclei have been studied and the possible structures for these bands are discussed.
Abstract: High spin states have been populated in 132,134Nd using the 104Pd(32S,2p2n)132Nd and 104Ru(34S,4n)134Nd reactions at 152 and 150 meV respectively. Several new states have been observed in both the yrast and negative-parity sidebands in these nuclei, In 132Nd a new band, probably built on a four-quasiparticle configuration, has been observed to feed into the yrast band at spin 10+. The present work focuses attention on the negative-parity sidebands in both nuclei. These are expected to have a proton structure based on a pi h11/2(X) pi g7/2 configuration. However, the bands display anomalously low crossing frequencies for the expected alignment of the second and third h11/2 protons (BC crossing). The possible structures for these bands are discussed.

12 citations

Journal ArticleDOI
TL;DR: Mean lifetimes have been measured for states up to Ipi =18+ in the yrast band of 132Ce using the recoil distance method in this article, which contrasts with the anomalously high B(E2) values measured in 130Ce.
Abstract: Mean lifetimes have been measured for states up to Ipi =18+ in the yrast band of 132Ce using the recoil distance method. In the vicinity of the first backbend, caused by the alignment of a pair of h11/2 protons, a pronounced drop in the collectivity is observed. This contrasts with the anomalously high B(E2) values measured in 130Ce. The results are compared with the theoretical predictions of the MONSTER code.

12 citations


Cited by
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01 Apr 2001
TL;DR: In this paper, the reduced electric quadrupole transition probability, B(E2)↑, from the ground state to the first-excited 2+ state of even-even nuclides are given in Table I.
Abstract: Adopted values for the reduced electric quadrupole transition probability, B(E2)↑, from the ground state to the first-excited 2+ state of even–even nuclides are given in Table I. Values of τ, the mean life of the 2+ state; E, the energy; and β, the quadrupole deformation parameter, are also listed there. The ratio of β to the value expected from the single-particle model is presented. The intrinsic quadrupole moment, Q0, is deduced from the B(E2)↑ value. The product E×B(E2)↑ is expressed as a percentage of the energy-weighted total and isoscalar E2 sum-rule strengths. Table II presents the data on which Table I is based, namely the experimental results for B(E2)↑ values with quoted uncertainties. Information is also given on the quantity measured and the method used. The literature has been covered to November 2000. The adopted B(E2)↑ values are compared in Table III with the values given by systematics and by various theoretical models. Predictions of unmeasured B(E2)↑ values are also given in Table III.

955 citations

Journal ArticleDOI
TL;DR: In this article, the decay of 132La to 132Ba has been studied in several works, including some recent papers, but in the opinion of the evaluators, this decay scheme still suffers from incompleteness, especially from the point of view of separate level schemes from the ground state and the isomeric activities.

176 citations

Journal ArticleDOI
TL;DR: In this article, experimental data on ground and excited-state properties for all known nuclei with mass number A = 134 have been compiled and evaluated, and level and decay schemes, as well as tables of nuclear properties are given.

108 citations

Journal ArticleDOI
TL;DR: In this article, a complete update of previous evaluations of A = 131 was presented together with adopted energies and Jπ of levels in these nuclei, including superdeformed and highly deformed structures in two SD bands and in two HD bands.

93 citations

Journal ArticleDOI
TL;DR: In this paper, the signature inversion in the pi h(11/2) x vi(13/2 ) bands of the odd-odd Tb, Ho and Tm nuclei was investigated.

84 citations