Virtual mechanism of ternary fission

It is shown that the experimental energy characteristics of long-range $\alpha$-particles, considered as third particles, emitted in the ternary spontaneous and induced by neutrons fission of nuclei allow us to assume that the ternary nuclear fission belongs to the class of two-stage virtual nuclear decays, in which states of intermediate nuclei that lie outside the mass surface of the decay appear, so as in previously studied processes of double beta-decay and two-proton decay of nuclei. The ternary fission widths and the $\alpha$-particles energy distributions were calculated based on the concepts of the quantum fission theory and the proposed virtual mechanism of ternary fission, taking into account that the $\alpha$-particle is emitted from the neck of the fissile nucleus in its configuration preceding the nucleus rupture into fission fragments. An estimate of the radius of the fissile nucleus neck for spontaneous ternary fission of $^{250,252}$Cf, $^{248}$Cm, nuclei, as well as for ternary fission of $^{233,235}$U nuclei induced by neutrons is obtained from the comparison of these energy distributions with experimental α-particles distributions and is consistent with the values of similar radii from calculations of the evolution of the fissile nucleus shape based on the generalized droplet model of the nucleus.