Abstract No:	015
Submitted on:	27 Dec 2000, 10:12 GMT
Title:	Search for magnetic rotation in the A 140 region.
Author(s):	T. Rzaca-Urban1 in collaboration with research groups from IKP Jülich, LNL Legnaro, Universities of Warsaw, Padova and Bonn.
Affiliation(s):	1Institute of Experimental Physics, University of Warsaw, Poland

In the early 1990's, a new type of rotation, represented by the rotation of a large magnetic dipole around the nuclear spin, has been discovered in Pb nuclei with A200. To date, such bands have been found in different nuclei in several mass regions [1]. Magnetic rotation (MR) is expected in weakly deformed nuclei close to magic numbers, if high-j particle orbitals and high-j hole orbitals are active [2]. In this work we will present recent data for several nuclei from the Z64 and N82 region obtained with -ray arrays EUROBALL and GASP at the Legnaro National Laboratory. Dipole magnetic bands, with strong M1 and weak or unobserved E2 crossover transitions, have been identified in ^142,143,144Gd and ¹⁴¹Eu nuclei. In general, a reasonable agreement between the experimental data and the predictions of the tilted axis cranking (TAC) model has been obtained supporting the interpretation of the dipole bands in this region as MR bands. Information about the strength of the effective interaction between constituent nucleons has been deduced using a semiclassical scheme of the coupling of two angular momentum vectors. A transition from regular to irregular MR bands has been found in Gd nuclei with N approaching 82. This can be explained as a decrease of quadrupole polarizability close to the magic shell, where short range residual interactions between valence particles dominate, which do not favour the formation of stable ''shears blades''.

Bibliography

1

R.M. Clark and A.O. Macchiavelli, Annu. Rev. Nucl. Part. Sci., 50, 1 (2000).

2

S. Frauendorf, Rev. Mod. Phys. In press (2000).