Search for Ra-226 spontaneous fission and systematics of the probabilitiesof spontaneous fission, alpha decay, and cluster decay

A lower limit on the half-life T-1/2 of Ra-226 With respect to spontaneous fission has been measured at a level of 4 x 10(18) yr. The probability of R a-226 spontaneous fission proved to be about 50 times less than the value e xpected from the known systematics relating the ratio of the alpha-decay an d spontaneous-fission probabilities to the fissility parameter Z(2)/A. It h as been shown that the probabilities of spontaneous fission, alpha decay, a nd cluster decay of 88 less than or equal to Z less than or equal to 100 ev en-even nuclei admit a unified systematization in terms of the difference o f the Coulomb energy in the vicinity of the scission point, V-Coul, and dec ay energy Q.