  An approximate SU(3) symmetry appears in heavy deformed even-even nuclei, by
omitting the intruder Nilsson orbital of highest total angular momentum and
replacing the rest of the intruder orbitals by the orbitals which have escaped
to the next lower major shell. The approximation is based on the fact that
there is a one-to-one correspondence between the orbitals of the two sets,
based on pairs of orbitals having identical quantum numbers of orbital angular
momentum, spin, and total angular momentum. The accuracy of the approximation
is tested through calculations in the framework of the Nilsson model in the
asymptotic limit of large deformations, focusing attention on the changes in
selection rules and in avoided crossings caused by the opposite parity of the
proxies with respect to the substituted orbitals.
