| Popis: |
Spectra of prompt internal conversion electrons with energies up to 2 MeV were obtained from targets of 159Tb, 165Ho, 169Tm, 175Lu and 181Ta bombarded with 12 MeV protons. Gamma-electron coincidence spectra were also measured. Most of the observed lines in the region around 1 MeV have been ascribed to decays from vibrational bands populated by the (p, 2n) reaction. Quadrupole vibrations with K = 2 have been found in 158Dy (945 keV), 164Er (857 keV) and 168Yb (986 keV). Bands with K = 0 were found in 158Dy (991 keV), 164Er (1238 keV), 168Yb (1156, 1197 and 1543 keV), 174Hf (827 keV) and 180W (908 keV). The K = 0 assignment was made on the basis of an E0 component in the decay. The rotational bands were populated up to levels with spin six or more. The spacing of energy levels in the vibrational bands indicates an increase in the moment of inertia as a function of the spin similar to that of the ground-state bands. In the gamma bands there is also a small relative displacement of even and odd spin levels. Mising of the excited and ground-state bands has been calculated from the E2 branching ratios, but accounts for only a small fraction of the energy depression in the ground state rotational bands. |
