Elsevier

Nuclear Physics A

Volume 228, Issue 3, 19 August 1974, Pages 493-512
Nuclear Physics A

The 186W(n, γ)187W reaction at 24 keV, hexadecapole deformations, and fragmentation of Nilsson model strength

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Abstract

The (n, γ) reaction at 24 keV and thermal neutron energies was performed on enriched samples of 186W to determine specific spin-parity limitations on states in the 700–1600 keV energy region in 187W. A number of these states are populated by some of the strongest transitions previously observed in the 186W(d, p)187W reaction. Comparison of the results of the two reactions yields information on the distribution and fragmentation of Nilsson single quasiparticle strengths. As in the odd Hf nuclei and in 183, 184w, significant fragmentation of strength was observed in 187W. The systematics of the fragmentation is presented and it is shown that a substantial loss of strength occurs in 183, 184W but not in 179Hf or 187W. The fragmentation, and its unexpected systematics, are not explained by previously available calculations. It is proposed that large hexadecapole deformations may be important in understanding the fragmentation. Such shape components lead to single particle energy shifts, enhanced ΔN = 2 and Coriolis mixing as well as other j-dependent effects that tend in the direction of the experimental results. Calculations are performed to illustrate these effects.

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    Work supported by the US Atomic Energy Commission.

    ††

    On leave from Technical University Munich, Mucnich, Germany.

    Now at National Bureau of Standards, Washington, DC 20234.

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