Nuclear field theory and highly forbidden nuclear decays: the case of 123Te

In this paper we apply Nuclear Field Theory techniques to describe the 123Te K-electron capture, whose half-life is reported to be the longest one ever measured in a single β decay. The theoretical half-life we obtain varies in the range (6.0 × 1019 − 8.9 × 1019)yr, which overestimates by a factor 3–4 the experimental one.