  A regular pattern, revealing the leading role of the light-fragment nuclear
charge, is found to emerge from a consistent analysis of the experimental
information collected recently on low-energy asymmetric fission of
neutron-deficient nuclei around lead. The observation is corroborated by a
theoretical investigation within a microscopic framework, suggesting the
importance of proton configurations driven by quadrupole-octupole correlations.
This is in contrast to the earlier theoretical interpretations in terms of
dominant neutron shells. The survey of a wider area of the nuclear chart by a
semi-empirical approach points to the lack of understanding of the competition
between the different underlying macroscopic and microscopic forces in a
quantitative manner. Combined with previously identified stabilizing forces,
the present finding shows a striking connection between the "old" (actinide)
and "new" (pre-actinide) islands of asymmetric fission which could steer the
strive for an unified theory of fission.
