Structure of odd–odd 136La at high spin

The high spin states in the N = 79 odd–odd 136 La nucleus have been investigated by in-beam γ -spectroscopic techniques following the 130 Te( 11 B, 5 n ) 136 La reaction at E = 52 MeV using an array, consisting of eight Compton-suppressed clover germanium detectors. Thirty nine new γ rays have been assigned to 136 La on the basis of γ ray singles and γγ -coincidence data. The level scheme of 136 La has been extended above the known 115 ms isomer upto an excitation energy of 4.6 MeV and spin 18 ℏ . 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.