  Proton inelastic scattering experiments at energy E_p = 200 MeV and a
spectrometer scattering angle of 0 degree were performed on 144,146,148,150Nd
and 152Sm exciting the IsoVector Giant Dipole Resonance (IVGDR). Comparison
with results from photo-absorption experiments reveals a shift of resonance
maxima towards higher energies for vibrational and transitional nuclei. The
extracted photo-absorption cross sections in the most deformed nuclei, 150Nd
and 152Sm, exhibit a pronounced asymmetry rather than a distinct double-hump
structure expected as a signature of K-splitting. This behaviour can be related
to the proximity of these nuclei to the critical point of the phase shape
transition from vibrators to rotors with a soft quadrupole deformation
potential. Self-consistent random-phase approximation (RPA) calculations using
the SLy6 Skyrme force provide a relevant description of the IVGDR shapes
deduced from the present data
