Electromagnetic decay properties of high spin states in 4391Tc48.

Abstract

High spin states in the nucleus Tc-91 have been studied via the fusion evaporation reaction Ni-58(Ar-36,3p)Tc-91, at 149 MeV and 140 MeV beam energy. The OSWS spectrometer, an additional high purity Ge detector at 162 degrees, and several particle detectors were used to measure gamma gamma- and particle-gamma coincidences, directional correlations of oriented states, and line shapes due to Doppler-shift attenuation. Lifetimes in the 10(-12)-10(-9) S range were measured by the recoil distance Doppler-shift method. Some 110 transitions were placed into a level scheme comprising 51 levels reaching up to 12.2 MeV excitation energy and a possible spin I = 49/2 h ($) over bar. A large number of spin-parity assignments and E2/M1 mixing ratios and lifetimes were deduced. This extensive data set is used for a detailed test of shell model calculations. They were performed with different sets of parameters, within either a restricted pi(p(1/2)), pi(g(9/2)), nu(p(1/2)), and nu(g(9/2)) configuration space or an enlarged configuration space including the pi(p(3/2)) and pi(f(5/2)) orbits. (Less)