  Isoscalar dipole strength distributions in spherical medium- and heavy-mass
nuclei are calculated within random phase approximation (RPA) or quasiparticle
RPA. Different Skyrme-type interactions corresponding to incompressibilities in
the range 200 - 250 MeV are used. The results are discussed in comparison with
existing data on isoscalar giant dipole resonances. Two main issues are raised,
firstly the calculated giant resonance energies are somewhat higher than the
observed ones, and secondly a sizable fraction of strength is predicted below
20 MeV which needs to be experimentally confirmed.
