Fragment Spin-Alignment in Fission

 
Figure: A schematic illustration of the alignment of fragment spins perpendicular to the fission direction.

     ²⁵²Cf spin J=0
fragment spin J=<7-8>

Mean number of -rays emitted in ²⁵²Cf fission <N>=9.4   [K.Skarsvag,Phys.Rev.C22(1980),638]

It is well known that the fragment spins J are relatively high even for the Fragment spin vectors are mainly oriented perpendicular to the fission direction. This alignment causes the emission of the yrast -rays to proceed anisotropically with respect to the fission axis. The most probable reason for fragment spins and their alignment is the excitation of collective vibrational modes like bending or wriggling at the saddle-to scission stage.