Enhanced B(E3) Strength Observed In La-137

The La-137 nucleus was populated by the reaction Te-130(B-11, 4n) at 40-MeV beam energy and the lifetime of the 11/2(-) state at 1004.6 keV was measured using a hybrid array of HPGe clover and LaBr3 (Ce) detectors by electronic fast-timing technique, providing the value T-1/2 = 263 +/- 12 ps. The reduced transition probability B(E3) = 23.3 +/- 2.4 W.u. is found to be significantly larger compared to the values observed in lighter odd-A La isotopes. The experimentally determined B(E3) value is compared with theoretical calculations of random-phase approximation which explains the enhanced transition probability to be arising from higher contribution of the g(9/2) orbital to the proton transition density.