Decay of the very neutron-deficient isotope Pm-131

The decay of Pm-131 has been investigated by means of gamma-ray spectroscop y. The Pm-131 nuclei were produced by fusion-evaporation reaction of Cd-106 (S-32,3p4n) at the beam energy of 170 MeV. A helium-jet technique and a tap e transport system were used to collect the activities and transfer them to a detecting position for X and gamma rays measurement. Two gamma rays of 1 85.0 and 220.0 keV were unambiguously identified to follow the beta(+) deca y of Pm-131 by results of X-gamma and gamma-gamma coincidence. A growth-dec ay feature of the decay curve for 87.8 keV gamma-ray of Nd-131 confirmed th e production of Pm-131 nuclei. The half-life of Pm-131 was measured to be 6 .3+/-0.8 s. A partial decay scheme of Pm-131 is proposed on the basis of X- gamma and gamma - gamma coincidence data in this experiment and the known s tructure information deduced from in-beam experiments of the daughter nucle us Nd-131.