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Bochum 1998 – scientific programme

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HK: Hadronen und Kerne

HK 50: Spectroscopy: 130 ≤ A ≤ 180

HK 50.8: Group Report

Wednesday, March 18, 1998, 16:15–16:45, D

New insights in the first backbending region of heavy Dy-isotopes — •T. Härtlein1, H. Bauer1, B. Binder1, A. Dietrich1, Ch. Gund1, D. Pansegrau1, D. Schwalm1, A. Jungclaus2, G. Hagemann3, D. Napoli4, S. Lunardi4, G. de Angelis4, C. Ur4, and A. Gadea41MPI für Kernphysik Heidelberg — 2Uni Göttingen — 3NBI Kopenhagen — 4INFN Legnaro

The interpretation of the first backbend in deformed rare earth nuclei as a crossing of the ground state band with a rotational band built on an aligned i13/2 neutron pair is rather well established. Especially in the light neutron deficient nuclei, this picture is rather successful and the crossing frequency as well as the oscillating behaviour of the interaction strength when filling the i13/2 neutron shell is readily understood in the framework of cranked shell model [1]. However, in more neutron rich nuclei like 160/162Dy, some additional aspects occour, which do cannot be explained in the usual picture. For example in 162Dy, the crossing frequency of the first backbend is shifted upwards by 50 keV to ℏ ωc ≈ 320 keV what is an unexpected behaviour for a nucleus in that mass region. Furthermore, in Coulomb excitation of 160Dy, an exclusive population of yrast states in and above the backbending region is observed, which cannot be explaind in terms of a two band mixing model [2]. Therefore two complementary types of experiments were performed during the german CLUSTER campaign and at GASP, to get detailed and more complete information about the nuclear structure in the region of the first backbend. Using the incomplete fusion reaction 158/160Gd(7Li,xn and pxn), it was possible for the first time to populate the rather n-rich nuclei 159−162Ho and 160−163Dy with angular momentum up to 28ℏ and thereby to extend our knowledge about the i13/2-qp band and further interacting bands over a wide range. Using Coulomb excitation, which is a coherent and diabatic process, additional information about the wave functions of the interesting states and the phases of the connecting matrix elements could be obtained.
supported by BMBF
[1] G. B. Hagemann, I. Hamamoto, Phys. Rev. C46, 838 (1992)
[2] T. Härtlein et al., Prog. Part. Nucl. Phys. 38, 309 (1997)

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