Double Beta Decay to Excited States of Daughter Nuclei

Abstract

In this paper we review results obtained in the searches of double beta decays to excited states of the daughter nuclei and illustrate the related experimental techniques. In particular, we describe in some detail the only two cases in which the transition has been observed; that is the 2β−(0+→01+) decay of 100Mo and 150Nd nuclides. Moreover, the most significant results in terms of lower limits on the half-life are also summarized.

Enriched Crystal Scintillators for 2β Experiments

“…The average values of the half-lives relative to 2ν2β decay are shown in Figure 1 (black squares). The 2ν2β decay to the first 0 + excited level of the daughter nucleus in 100 Mo and 150 Nd has also been detected with half-lives of T 1/2~1 0 20 years [5,6]. The processes of 2β decay with nuclear charge decreasing have been observed only for 124 Xe [7] and 78 Kr [8] in direct experiments, but also for 130 Ba in geochemical experiments [9,10].…”

“…106 CdWO 4 crystal scintillator (1) is viewed through the PbWO 4 light-guide (2) with the help of Photomultiplier Tube (PMT) (3). Two CdWO 4 crystal scintillators (4) are viewed by two PMT (7) through optical light-guides composed of two parts: Ultrapure quartz (5) and polystyrene(6). The passive shield consists of copper (8-some parts are shown), lead, polyethylene, and cadmium.…”

Status and Perspectives of 2ϵ, ϵβ+ and 2β+ Decays

“…This motivated the DAMA and DAMA-INR Kyiv efforts. Besides this, the intriguing possibility to either develop or improve new low background crystal scintillators for both rare event investigations and industrial/medical applications has further motivated different DAMA and DAMA-INR Kyiv R&Ds [30,42,50,55,59]. Table 3 shows the best limits that are mainly achieved using crystal scintillator detectors, besides those already listed in Tables 1, 2 and 4.…”

“…The DAMA-INR Kyiv collaboration holds the most stringent limits for mostly all of the isotopes investigated by this technique. Thus, in this Section, we briefly summarize the measurements that were carried out by the HPGe γ spectrometers at the STELLA facility of LNGS [232] by the DAMA-INR Kyiv collaboration (also see [42,59] and the References therein).…”

“…To this purpose, there are different experimental approaches, such as those that are capable of distinguishing-while properly accounting for the energy resolution-the beta spectrum of the 0ν and 2ν modes or those that are able to detect the gamma emitted from the excited final states (see also, e.g., Reference [42] for DBDs in excited states and Reference [19] for 2 decay modes).…”