Double beta decay of 150Nd to the first excited 0+ level of 150Sm: preliminary results

The double beta decay of 150Nd to the first excited 0+ level of 150Sm (E_exc = 740.5 keV) was investigated with the help of the ultra-low-background setup consisting of four HP Ge (high-purity germanium) detectors (≃225 cm3 volume each one) at the Gran Sasso underground laboratory of INFN (Italy). A highly purified 2.381-kg sample of neodymium oxide (Nd2O3) was used as a source of γ quanta expected in the decays. Gamma quanta with energies 334.0 keV and 406.5 keV emitted after deexcitation of the 0^1_+ 740.5 keV level of 150Sm are observed in the coincidence spectra accumulated over 16375 h. The half-life relatively to the two neutrino double beta decay 150Nd → 150Sm(0^1_+) is measured as T_!/2 =[4.7^+4.1_ -1.9 (stat ) +/- 0.5(syst)] x 10^19 y, in agreement with previous experiments.