Double-Beta Decay of <super>150</super>Nd to Excited Final States
An experimental study of the two-neutrino double-beta (2νββ) decay of <super>150</super>Nd to various excited final states of <super>150</super>Sm was performed at Triangle Universities Nuclear Laboratory (TUNL). Such data provide important checks for theoretical models used to predict 0νββ decay half lives.
The measurement was performed at the recently established Kimballton Underground Research Facility (KURF) in Ripplemeade, Virginia using the TUNL-ITEP double-beta decay setup. In this setup, two high-purity germanium detectors were operated in coincidence to detect the deexcitation gamma rays of the daughter nucleus. This coincidence technique, along with the location underground, provides a considerable reduction in background in the regions of interest.
This study yields the first results from KURF and the first detection of the
coincidence gamma rays from the 0<super>+</super>1 excited state of <super>150</super>Sm. These gamma rays
have energies of 334.0 keV and 406.5 keV, and are emitted in coincidence through a 0<super>+</super>1→2<super>+</super>1→0<super>+</super>gs transition. The enriched Nd2O3 sample obtained from Oak Ridge
National Laboratory consists of 40.13 g <super>150</sub>Nd. This sample was observed for 391 days, producing 29 raw events in the region of interest. This count rate gives a half life of T1/2 = (0.72<super>+0.36</super>−0.18 ± 0.04(syst.)) × 10<super>20</super> years, which agrees within error with
another recent measurement, in which only the single deexcitation gamma rays were detected (i.e., no coincidence was employed). Lower limits were also obtained for decays to higher excited final states.
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