Structure of even-even 138Nd from the decay of 138Pm

The structure of 138Nd is investigated through the β+-decay of 138Pm, whose decay half-life is measured to be 3.24 +- 0.05 min. A level structure comprising 27 excited states and 52 transitions is constructed. With the help of deduced ft values and internal conversion coefficients, spin-parity assignments are made to many states in 138Nd and to the ground states of 138Pm. From the positron end-point energy measurement, the total decay energy is determined to be 5.4 +- 0.2 MeV, which is compared with the predictions of several mass formulae and with the decay energy systematics of the N = 77 isotones. The structure of 138Nd is discussed in the light of nuclear systematics of the N = 78 isotones. (orig.)