Energy resolution, a=b ratio, and the pulse shape discrimination ability of the ZnWO 4 crystal scintillators were studied. The radioactive contamination of a ZnWO 4 crystal was investigated in the Solotvina Underground Laboratory. Possibilities to apply ZnWO 4 crystals for the dark matter and double beta decay searches are discussed. New improved half-life limits on double beta decay in zinc isotopes were established, in particular, for eb þ decay of 64 Zn as: T 2n 1=2 X8:9 Â 10 18 years and T 0n 1=2 X3:6 Â 10 18 years, both at 68% CL. r

β decay of 113 Cd was studied with the help of a low background CdWO 4 crystal scintillator (mass of 434 g) in an experiment at the Gran Sasso National Laboratories of the INFN for a period of 2758 h. The shape of the spectrum of the non-unique fourth-forbidden decay of 113 Cd was measured, and the half-life of 113 Cd was determined as T 1/2 = (8.04 ± 0.05) × 10 15 yr.

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Double beta processes in 64 Zn, 70 Zn, 180 W, and 186 W have been searched for with the help of large volume (0.1 − 0.7 kg) low background ZnWO 4 crystal scintillators at the Gran Sasso National Laboratories of the INFN. Total time of measurements exceeds 10 thousands hours. New improved half-life limits on double electron capture and electron capture with positron emission in 64 Zn have been set, in particular (all the limits are at 90% C.L.): T 0ν2ε 1/2 ≥ 1.1 × 10 20 yr, T 2νεβ +