First observation of spontaneous fission and search for cluster decay of 232Th

We present results of a long-term search for cluster (neon) decay and spontaneous fission of ²³²Th performed at Gran Sasso Underground Laboratory with nuclear track detectors. We found a lower limit for the partial half-life for ^24-26Ne decay, T_1/2>1.57×10²⁹ s and a partial half-life for spontaneous fission T_1/2=3.84×10²⁸ s=1.22×10²¹ yr. These results are compared with the available theoretical predictions and the experimental systematics for cluster decay and spontaneous fission.