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##

Coulomb effects and isospin symmetry

An important observation that follows from a comparison of Figs. 1
and 2 is that the neutron and proton routhian spectra are almost
identical, apart from a nearly constant shift in energy that amounts to about
6MeV. Such a constant shift expresses the fact that despite a possibly
non-trivial evolution of the individual-nucleonic wave functions in terms of
the rotational frequency, the corresponding Coulomb interactions average out
to nearly a constant,
and correspond to the
Coulomb energy of a rotating but otherwise
-independent
charge distribution.

On the one hand, degeneracy of neutron and proton routhians
is a manifestation
of a charge-independence of the forces used. On the other hand,
however, the pairs of nearly degenerate proton and neutron wave-functions may
be used to introduce an alternative representation in terms of the isoscalar-
and isovector-coupled wave-functions. In such a case any
arbitrary isospin-symmetric residual
interaction is likely to introduce systematic differences
in the spectra
of the *T*=0 and *T*=1 states.
This would allow to test that particular component of the forces
against experiment - or, conversely, from an existence of systematic discrepancies
between experiment and mean-field calculations - it would allow to optimize the
residual interactions. The observed near-degeneracy of the corresponding
proton and neutron levels is in fact a prerequisite
indication that in this mass region the isospin-symmetry
effects could be very important. We will use the above observation as a
guideline in further analysis of the neutron/proton
configurations in ^{32}S and neighboring nuclei.

** Next:** Classification of SD bands
** Up:** Single-particle structures at N=Z=16
** Previous:** Deformed shell gaps
*Jacek Dobaczewski*

*1999-07-27*