INTERACTION STRENGTH AND SHAPE DIFFERENCE FOR THE H9/2 AND H11/2 CONFIGURATIONS IN TM-163

The strongly shape driving pi-h9/2[541]1/2- configuration with alpha = + 1/2 exhibits some anomalous, and so far unexplained, features concerning the crossing frequency, HBAR-omega-c, the aligned angular momentum, i(x), and interaction strength, at the alignment of the first pair of i13/2 quasineutrons in several odd-Z rare earth-nuclei. The h9/2[541]1/2- and h11/2[523]7/2- bands have been studied in the stably deformed rare-earth nucleus Tm-163 to investigate these features. A difference in band crossing frequency of approximately 80 keV between the two bands is found. Rotational bands built on these two configurations have been found to cross in the spin range I = 25/2 - 29/2 HBAR. The gamma-decay pattern between the two bands is established in the crossing region and analysed in terms of a moderate shape difference between them. A theoretical estimate of the size of the interaction strength between the two bands is presented and compared to the experimental value. The observed band structure in Tm-163 is very similar to that of Lu-167 which has 2 protons and 2 neutrons in addition. This observation is discussed in relation to the similarity of the yrast bands of the two even-even "core" nuclei Er-162 and 166Yb, for which the gamma-transition energies are identical within approximately 0.2 keV below the nu-i13/2 crossing.