Double beta decay of 150Nd to the excited levels of 150Sm

AbstraktAbstract

The search for double beta decay of Nd-150 to the excited levels of Sm-150 was performed at the Gran Sasso underground laboratory of INFN (Italy) with a four-crystal HPGe gamma spectrometer over 5.845 yr by using a highly purified neodymium-containing sample. The two-neutrino double beta transition of Nd-150 to the first 740.5 keV 0(+) level of Sm-150 was detected in both one-dimensional and coincidence spectra with a half-life..1/2 = [0.83(-0.13)(+0.18) ( stat)(+0.16)(-0.19) (syst)] x10(20) yr, in agreement with the results of the previous experiments. Some excess of the 334.0-keV peak is observed that is an indication of the 2 nu 2 beta decay of 150Nd to the 334.0 keV 2(+) excited level of 150Sm with the half-life..1/2 = [ 1.5(+2.3) (- 0.6) (stat)+/- 0.4(syst)] x1020 yr, that leads also to slightly higher half-life for the 0+ to 0+ 1 transition:..1/2 = [1.03+0.35 -0.22 ( stat)+0.16 -0.19 (syst)] x 1020 yr. The half-life value for the 0+ to 2(1)(+) decay does not contradict the existing limits and agrees with the half-life range calculated in the framework of proton-neutron QRPA with isospin restoration combined with like-nucleon QRPA for a description of excited states in the final nuclei. A possible advancement in experimental sensitivity is briefly discussed.

The search for double beta decay of Nd-150 to the excited levels of Sm-150 was performed at the Gran Sasso underground laboratory of INFN (Italy) with a four-crystal HPGe gamma spectrometer over 5.845 yr by using a highly purified neodymium-containing sample. The two-neutrino double beta transition of Nd-150 to the first 740.5 keV 0(+) level of Sm-150 was detected in both one-dimensional and coincidence spectra with a half-life..1/2 = [0.83(-0.13)(+0.18) ( stat)(+0.16)(-0.19) (syst)] x10(20) yr, in agreement with the results of the previous experiments. Some excess of the 334.0-keV peak is observed that is an indication of the 2 nu 2 beta decay of 150Nd to the 334.0 keV 2(+) excited level of 150Sm with the half-life..1/2 = [ 1.5(+2.3) (- 0.6) (stat)+/- 0.4(syst)] x1020 yr, that leads also to slightly higher half-life for the 0+ to 0+ 1 transition:..1/2 = [1.03+0.35 -0.22 ( stat)+0.16 -0.19 (syst)] x 1020 yr. The half-life value for the 0+ to 2(1)(+) decay does not contradict the existing limits and agrees with the half-life range calculated in the framework of proton-neutron QRPA with isospin restoration combined with like-nucleon QRPA for a description of excited states in the final nuclei. A possible advancement in experimental sensitivity is briefly discussed.