The Aurora experiment at the underground (3600 m w.e.) Laboratori Nazionali del Gran Sasso (INFN, Italy) investigated double beta decay of 116Cd with the help of 1.16-kg cadmium tungstate crystal scintillators enriched in 116Cd to 82% (116CdWO4). The half-life of 116Cd relative to the 2ν2β decay to the ground state of 116Sn was measured with the highest up-to-date accuracy as T1/2 = 2.63 +0.11–0.12 × 1019 yr. A new limit on the 0ν2β decay of 116Cd to the ground state of 116Sn was set as T1/2 ≥ 2.2 × 1023 yr at 90% C.L., which is the most stringent known restriction for this isotope. The data collected with highly radiopure 116CdWO4 crystal scintillators during 26831 h was decided to be also used for a search of long-lived superheavy ekatungsten at the high energy part of the measured α spectrum. The limit obtained in these measurements is in agreement with those obtained in recent experiments which instead look for spontaneous fission of superheavy elements or use the accelerator mass spectrometry.
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Oksana G. Polischuk
Institute for Nuclear Research
Kiev, Ukraine