COLLECTIVE EXCITATIONS IN THE TE-117,TE-119,TE-121 NUCLEI

High-spin states in odd-mass Te nuclei were studied by means of the (α, 2n), (3He, 3n) and (d, 2n) reactions. Using in-beam spectroscopic methods γ-ray energies, intensities, excitation functions, time and angular distributions and γ-γ coincidences were measured. Also, for 121Te, measurements of the linear polarization of γ-rays and internal conversion electron spectra were performed. Level schemes of odd-mass Te nuclei (A = 117-121) were established Up to spin values of J = 23 2. The predominantly excited level sequences, built on the 11 2- states, are compared with the ground state bands in doubly even Te nuclei. The systematics of decoupled 11 2- bands in the Z = 50 region is given. Deviations of the level spacings for maximum aligned states of the h 11 2 ⊗ R multiplets from those of the g.s. bands in the neighbouring core nuclei can be observed. The energetically favoured coupling to Jmax -1 may be caused by the blocking effect due to the Pauli principle or by dynamical shape fluctuations. The h 11 2 level systems of the Te nuclei are furthermore compared with particle-core coupling calculations where different models for the core are tested, such as the rigid triaxial rotor, the soft rotor including hexadecapole deformation, and the γ-unstable potential. Each model assumption leads to a rather good agreement with the experimental level energies. © 1979.