Soliton excitations as emitted clusters on nuclear surfaces
This work reports on calculations of the deformation energy of a nucleus for nonlinear deformations. The working hypothesis is that, beyond the usual linear approximation, the nonlinear analysis yields soliton solutions moving on its surface. The potential barrier against the emission of a soliton is calculated within the macroscopic-microscopic method. The outer turning point of the barrier determines limitations on the geometrical and kinematical parameters for the formation of a surface soliton. For large asymmetry, the two-centre shell model is used to assign a structure to the soliton. Calculations for 248No with the emission of a 40Ca soliton are reported; likewise for 224Th with the emission of 16O. Except for necked shapes at the very first stages of soliton formation, the greatest portion of the deformation path displays rather compact configurations with large neck radii. These shape sequences correspond to allowable soliton velocities. Close to and just beyond the touching point configuration, where the shape becomes concave, the width and the velocity of the soliton approaches zero. The calculations suggest that the emission of a 40Ca structure is quite probable due to a low potential barrier, whereas the emission of an 16O-type soliton is rather unlikely due to the higher penetration barrier.