High-spin structures of 13857La81.

Odd-odd 138La nuclei have been produced in the 12C+238U fusion-fission reaction and their γ rays studied with the Euroball array. The high-spin level scheme has been built up to ~4.5 MeV excitation energy and spin I~16h from the triple γ-ray coincidence data. An isomeric state lying at 739-keV excitation energy has been identified. The configurations of the structures are first discussed by analogy with the proton excitations identified in the semimagic 139La82 nucleus, which involve the three high-j orbits lying above the Z=50 gap, pg7/2, pd5/2, and ph11/2. The competition of these three orbits to produce the yrast line is confirmed by the results of shell-model calculations performed in this work. [ABSTRACT FROM AUTHOR]