A Study of the 190 keV Transition in 141La

The gamma-ray spectrum from the decay of 18 min 141 Ba has been studied. Seventeen transitions were found below 900 keV, with energies and (intensities) as follows: 112.9±0.2(3.0), 163.1±0.3 (1.0), 165.7±0.4(0.7), 180.5±0.2(0.9), 190.3±0.1(100), 276.9±0.1 (52.2), 304.2±0.1(55.8), 343.6±0.1(30.8), 364.4±0.6(1.6), 389.7±0.2(2.8), 457.7±0.2(10.4), 462.3±0.2(10.5), 467.3±0.1(11.4), 625.1±0.2(6.1), 647.9±0.2(10.7), 739.1±0.3(8.7), 876.5±0.3(6.7). K- and L-shell conversion coefficients have been measured for the 190. 3 keV transition, yielding a multipolarity of M1 + < 8 % E2. Half-life measurements using delayed coincidence technique have given the following results: T1/2 (190 keV level) 1.27 +0.06-0.10 ns, T1/2 (304 keV level) < 200 ps, T1/2 (467 keV level) < 120 ps. A level scheme of 141La has been constructed, and the spin-parity assignments of the ground state and first excited state are discussed in terms of the shell model