Structure of odd-odd 136La at high spin

The high spin states in the N = 79 odd-odd La-136 nucleus have been investigated by in-beam gamma-spectroscopic techniques following the Te-130(B-11, 5n)La-136 reaction at E = 52 MeV using an array, consisting of eight Compton-suppressed clover germanium detectors. Thirty nine new gamma rays have been assigned to 136La on the basis of gamma ray singles and gamma gamma-coincidence data. The level scheme of 136La has been extended above the known 115 ms isomer upto an excitation energy of 4.6 MeV and spin 18h. Thirty one new levels have been proposed and spin-parity assignments for most of the newly proposed levels have been made on the basis of the deduced asymmetry ratios and polarisation information for the de-exciting transitions. The observed positive parity yrast band has been compared with the theoretical calculation, done within the framework of particle rotor coupling model (PRM) where the two odd quasi-particles are coupled to an axially symmetric core. The level structure has been discussed in the light of the known systematics of the neighbouring N = 79 isotonic nuclei. (c) 2005 Elsevier B.V. All rights reserved.