High spin spectroscopy of 137La

Abstract We have studied the high spin states in the N = 80 137 La nucleus by in-beam γ -spectroscopic techniques following the reaction 130 Te( 11 B, 4 n ) 137 La at E beam = 52  MeV using an array, consisting of 8 Compton-suppressed Clover germanium detectors. Forty five new γ rays have been assigned to 137 La on the basis of γ ray singles, γγ doubles and γγγ triples coincidence data. Thirty eight new levels have been proposed and the level scheme of 137 La has been extended above the known 360 ns 19 2 − isomer up to an excitation energy of ∼ 6  MeV and spin 39 2 ℏ . The spin-parity assignments for most of the newly proposed levels have been made using the deduced directional correlation orientation and polarisation information for the de-exciting transitions. The new scheme consists, among others, two decay sequences having states with alternating parity connected by E1 transitions. An attempt has been made to understand these interesting structure by a modest shell model calculation.