The low-lying states and configurations in138La

Tritons from the reaction¹³⁹La(d, t)¹³⁸La atE _d=16 MeV were analyzed at eleven reaction angles from 22 ° to 90 ° with a broad-range magnetic spectrograph. TheQ-value of the reaction is ?2522±5 keV. The nine lowest-lying states in¹³⁸La are interpreted in terms of the shell model configurations (πg _7/2)^?1 (vd _3/2)^?1, (πg _7/2)^?1 (vs _1/2)^?1 and (πg _7/2)^?2 (πd _5/2)^?1(vd _3/2)^?1. Seven levels in the energy range of 700–1300 keV are populated byl=5 transitions and are interpreted as coming from the (πg _7/2)^?1(vh _11/2)^?1 configuration. The ground state of¹³⁸La is shown to haveJ ^π=5⁺. Therefore, beta decay by unique second-forbidden transitions to the 2⁺ one-phonon states of¹³⁸Ce and¹³⁸Ba must be inferred in spite of unusually high logft values of 19.2 and 18.5, respectively.