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

AbstraktAbstract

he 2 nu 2 beta decay of Nd-150 to the first excited 740.5 keV 0(1 )(+)level of Sm-150 was measured over 5.845 years with the help of a four-crystal low-background HPGe gamma spec-trometry system in the underground low-background laboratory STELLA of LNGS-INFN. A 2.381 kg highly purified Nd-containing sample was employed as the decay source. The expected de-excitation gamma-quanta of the 0(1)(+)levelwith energies 334.0 keV and 406.5 keV were observed both in one-dimensional spectrum and in coincidence data resulting in the half-life T-1/2=[0.83(-0.13)(+0.18)(stat)(+0.16)(-0.19)(syst)]x10(20 )year. Interpreting an excess of the 334.0-keV peak area as an indication of the 2 beta decay of Nd-150 to the 334.0 keV 2(1)(+)excited level of Sm-150 with a half-life of T-1/2=[1.5(-0.6)(+2.3)(stat)+/- 0.4(syst)]x10(20 ) year, the 2 nu 2 beta half-life of Nd-150 for the transition to the 0(1 )(+)level is T-1/2=[1.03+0.35-0.22(stat)+0.16-0.19(syst)]x10(20 )year, in agreement with the previous experiments. Both half-life values reasonably agree with the theoretical calculations in the framework of proton-neutron QRPA with isospin restoration combined with like nucleon QRPA for description of excited states in the final nuclei. For 2 nu 2 beta and 0 nu 2 beta transitions of Nd-150 and 148Nd to several excited levels of Sm-150 and148Sm, limits were set at level of T-1/2>10(20 )-10(21)year.

he 2 nu 2 beta decay of Nd-150 to the first excited 740.5 keV 0(1 )(+)level of Sm-150 was measured over 5.845 years with the help of a four-crystal low-background HPGe gamma spec-trometry system in the underground low-background laboratory STELLA of LNGS-INFN. A 2.381 kg highly purified Nd-containing sample was employed as the decay source. The expected de-excitation gamma-quanta of the 0(1)(+)levelwith energies 334.0 keV and 406.5 keV were observed both in one-dimensional spectrum and in coincidence data resulting in the half-life T-1/2=[0.83(-0.13)(+0.18)(stat)(+0.16)(-0.19)(syst)]x10(20 )year. Interpreting an excess of the 334.0-keV peak area as an indication of the 2 beta decay of Nd-150 to the 334.0 keV 2(1)(+)excited level of Sm-150 with a half-life of T-1/2=[1.5(-0.6)(+2.3)(stat)+/- 0.4(syst)]x10(20 ) year, the 2 nu 2 beta half-life of Nd-150 for the transition to the 0(1 )(+)level is T-1/2=[1.03+0.35-0.22(stat)+0.16-0.19(syst)]x10(20 )year, in agreement with the previous experiments. Both half-life values reasonably agree with the theoretical calculations in the framework of proton-neutron QRPA with isospin restoration combined with like nucleon QRPA for description of excited states in the final nuclei. For 2 nu 2 beta and 0 nu 2 beta transitions of Nd-150 and 148Nd to several excited levels of Sm-150 and148Sm, limits were set at level of T-1/2>10(20 )-10(21)year.