  Background: Inelastic proton scattering at energies of a few hundred MeV and
very-forward angles including $0^\circ$ has been established as a tool to study
electric-dipole strength distributions in nuclei. The present work reports a
systematic investigation of the chain of stable even-mass Nd isotopes
representing a transition from spherical to quadrupole-deformed nuclei.
  Purpose: Extraction of the equivalent photo-absorption cross sections and
analysis of their fine structure in the energy region of the IsoVector Giant
Dipole Resonance (IVGDR).
  Method: Proton inelastic scattering reactions of 200 MeV protons were
measured at iThemba LABS in Cape Town, South Africa. The scattering products
were momentum-analysed by the K600 magnetic spectrometer positioned at
$\theta_{\mathrm{Lab}}=0^\circ$. Using dispersion-matching techniques, energy
resolutions of $\Delta E \approx 40 - 50$ keV were obtained. After subtraction
of background and contributions from other multipoles, the spectra were
converted to photo-absorption cross sections using the equivalent
virtual-photon method.
  Results: Wavelet-analysis techniques are used to extract characteristic
energy scales of the fine structure of the IVGDR from the experimental data.
Comparisons with the Quasiparticle-Phonon Model (QPM) and Skyrme Separable
Random Phase Approximation (SSRPA) predictions provide insight into the role of
different giant resonance damping mechanisms.
  Conclusions: Fine structure is observed even for the most deformed nuclei
studied. Fragmentation of the one particle-one hole ($1p1h$) strength seems to
be the main source of fine structure in both spherical and deformed nuclei.
Some impact of the spreading due to coupling of the two particle-two hole
($2p2h$) states to the $1p1h$ doorway states is seen in the
spherical/transitional nuclei, where calculations beyond the $1p1h$ level are
available.
