Sources of ${\mathrm{Ba}}^{131m}$ were produced by bombarding sodium iodide with ${\mathrm{Li}}^7$ ions of about 38-MeV energy, and its half-life was redetermined as 14.6±0.2 min. Its decay was studied by means of scintillation techniques. The decay of ${\mathrm{Ba}}^{131m}$ proceeds by a (78±5)-keV $E3\mathrm{}$ transition (${\alpha }_K=12.3\mathrm{}\pm 1.5$), followed by a (107±3)-keV $M1+E2\mathrm{}$ transition (${\alpha }_K=0.90\mathrm{}\pm 0.15$). Included is a discussion of possible spin and parity assignments for the levels involved in this decay. An auxiliary experiment showed that less than 1% of ${\mathrm{La}}^{131}$ decays lead to ${\mathrm{Ba}}^{131m}$.

• Received 17 September 1962

DOI:https://doi.org/10.1103/PhysRev.129.1712