ROTATIONAL BANDS IN THE MASS-100 REGION

Rotational bands up to spins of almost-equal-to 10HBAR have been studied in even-even and odd-A nuclei in the mass 100 region, by observing prompt gamma-rays from the spontaneous fission of Cm-248. Transitions in the neutron-rich nuclei 103Zr, 104Zr, 107Mo and 108Mo have been observed for the first time, and evidence for a band in 105Nb is presented. Rotational bands are also reported in 98-100Sr, 99-101Y 100-102Zr, 101-103Nb and 102-106Mo. In most cases these bands have been extended to much higher spins than previously known. The data on the even-even nuclei provide information on deformation trends in this region. The level structures of the odd-A nuclei indicate which Nilsson orbitals lie close to the Fermi level. Bands based on the 5/2+[422] and 5/2-[303] configurations are identified in the odd-A nuclei with Z = 39 and 41. Evidence is presented that certain bands observed in N = 61 and 63 nuclei are built on the 5/2-[532] configuration, and the role of the neutron h11/2 orbital in stabilizing the deformation in this region is discussed.