Theoretical approaches to the emission of α particles during nuclear fission

Recent models as well as new trajectory calculations used to interpret the experimental data on α-accompanied fission are presented and experimental hints towards the emission mechanism are pointed out. The important question of the distribution of the emission points and moments is brought up: are these particles coming only from the region between the fragments (the neck) or, are they coming with comparable probability, from any point of the surface of the fissioning system and: are they emitted just at scission or at any sufficiently deformed stage of the fission process. The simultaneous division of the nucleus into three fragments (the true ternary fission) is discussed in terms of the dynamical liquid-drop model. It is suggested that this process occurs in the tail (corresponding to overelongated shapes) of the distribution of the fission probability in the multidimensional space of the collective coordinates