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Title: K-Isomers and Aspects of Nuclear Structure

Abstract

Gamma-ray spectroscopy measurements with Gammasphere and multi-nucleon transfer reactions with heavy beams provide a means of accessing deformed nuclei at stability, or on the neutron-rich side of the stability line. New results on the discovery of high-K isomers in the Er-Tm-Yb-Lu region are discussed with a focus on the energy systematics and the factors which may govern K-purity and therefore K-hindrances. These include random-mixing in regions of high level density, specific Coriolis mixing in configurations involving the i13/2 neutron configuration, and chance degeneracies between an individual high-K state and a specific collective state which provide an opportunity to extract effective mixing matrix elements between states of very different-K.

Authors:
 [1]
  1. Department of Nuclear Physics, R.S.Phys.S.E., Australian National University, Canberra, A.C.T. 0200 (Australia)
Publication Date:
OSTI Identifier:
20798324
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 819; Journal Issue: 1; Conference: 12. international symposium on capture gamma-ray spectroscopy and related topics, Notre Dame, IN (United States), 4-9 Sep 2005; Other Information: DOI: 10.1063/1.2187827; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; DEFORMED NUCLEI; ENERGY-LEVEL DENSITY; GAMMA SPECTROSCOPY; ISOMERIC NUCLEI; LUTETIUM; MASS NUMBER; MATRIX ELEMENTS; MIXING; MULTI-NUCLEON TRANSFER REACTIONS; NEUTRONS; NUCLEAR STRUCTURE; STABILITY; THULIUM; YTTERBIUM

Citation Formats

Dracoulis, G. D.. K-Isomers and Aspects of Nuclear Structure. United States: N. p., 2006. Web. doi:10.1063/1.2187827.
Dracoulis, G. D.. K-Isomers and Aspects of Nuclear Structure. United States. doi:10.1063/1.2187827.
Dracoulis, G. D.. Mon . "K-Isomers and Aspects of Nuclear Structure". United States. doi:10.1063/1.2187827.
@article{osti_20798324,
title = {K-Isomers and Aspects of Nuclear Structure},
author = {Dracoulis, G. D.},
abstractNote = {Gamma-ray spectroscopy measurements with Gammasphere and multi-nucleon transfer reactions with heavy beams provide a means of accessing deformed nuclei at stability, or on the neutron-rich side of the stability line. New results on the discovery of high-K isomers in the Er-Tm-Yb-Lu region are discussed with a focus on the energy systematics and the factors which may govern K-purity and therefore K-hindrances. These include random-mixing in regions of high level density, specific Coriolis mixing in configurations involving the i13/2 neutron configuration, and chance degeneracies between an individual high-K state and a specific collective state which provide an opportunity to extract effective mixing matrix elements between states of very different-K.},
doi = {10.1063/1.2187827},
journal = {AIP Conference Proceedings},
number = 1,
volume = 819,
place = {United States},
year = {Mon Mar 13 00:00:00 EST 2006},
month = {Mon Mar 13 00:00:00 EST 2006}
}
  • Nuclear K-isomers play a pivotal role in understanding the structure of deformed, axially symmetric nuclei. Examples are presented of recent studies of exotic multi-quasiparticle isomers in the A{approx}180 rare-earth region at the extreme of angular momentum and neutron number. A specific band-mixing scenario is invoked to explain the unusual decay path of the K{pi}=57/2- isomer (T1/2=22 ns) in 175Hf, the highest spin K-isomer known in nature. The discovery of a suite of high-K isomers, above the previously known K{pi}=23/2- (T1/2=160 d) state in 177Lu, using deep-inelastic and multi-nucleon transfer reactions is discussed.
  • K isomers are studied in Pu and Cm isotopes, and also in Hf and W nuclei. Many high-K states, several of which are isomeric, are identified. Lifetime measurements spanning the ns-s range have been performed, and decay paths of isomers established. Rotational bands built on high-K states are also identified in many cases. Isomer decays are considerably hindered in many instances, both in the A≈180 and 250 regions indicating that K is an approximately conserved quantum number. High-K states become the favored excitation mode at high spins in the A≈180 region. The energies of the 2-quasiparticle high-K states in Cmmore » isotopes suggest the presence of a deformed subshell gap at N=152.« less
  • The authors have obtained the fluorescence fine-structure spectra for isomers of Zn-tetramethylporphyrin (TMP) (Zn-2, 3, 7, 8-TMP, Zn-2, 3, 12, 13-TMP, Zn-2, 8, 12, 18 TMP) in isotropic media at 4.2/sup 0/K with selective laser excitation. For the phononless lines in the spectra of the indicated isomers, they have measured the values of the degree of polarization and have determined the symmetry of the vibrations in the electronic ground state. They have carried out theoretical calculations of the frequencies and forms of the normal vibrations of the given compounds and have carried out simultaneous analysis of the theoretical and experimentalmore » results. They have considered the effect of the location of the four methyl groups on the electronic-vibrational spectra of Zn-TMP isomers. They have shown that in Zn-2, 3, 7, 8-TMP, the direction of the transition moment S/sub 0/ ..-->.. S/sub 1/ does not coincide with the symmetry axis of the molecules due to their interaction with the medium. They discuss the reasons for the splitting of the long-wavelength absorption band of Zn-alkylprophyrins having hydrogen atoms in ..beta.. positions of the pyrrole rings adjacent to one meso position.« less
  • No abstract prepared.