The measurement and its motivation

Armonia (meAsuReMent of twO-NeutrIno ββ decAy of 100Mo to the first excited 0+ level of 100Ru ) consists of a Molybdenum sample (mass ≈ 1 kg enriched in 100Mo at 99.5%) installed in the 4π low-background HP Ge detectors facility (4 HP Ge - about 225 cm3 each - mounted in one cryostat) located in the underground Ge facility of the National Laboratory of Gran Sasso.

The aim is to measure the 2β2ν decay of 100Mo to the first excited 0+1 level of 100Ru at E(0+1)=1130.5 keV by investigating the presence in the data of the 2 γ quanta, with energies of 590.8 keV and 539.5 keV, emitted in cascade in the deexcitation process.

Armonia, with its high sensitivity, allow either to confirm positive results (with T1/2 in the range around 6-9 x 1020 y) or to confirm previous higher limit value (T1/2 > 1.2 x 1021 y at 90% C.L.), both available in literature.