  The pygmy dipole resonances (PDR) for even-even nuclei in 8=<Z=<40 are
studied performing a systematic calculation of the random-phase approximation
with the Skyrme functional of SkM*. The calculation is fully self-consistent
and does not assume any symmetry in the nuclear shape of the ground state. In
every isotopic chain, the PDR emerges by showing a peak of the E1 strength at
energies less than 10 MeV. The E1 strength of the PDR strongly depends on the
position of the Fermi level and shows a clear correlation with the occupation
of the orbits with the orbital angular momenta less than 3\hbar (l =< 2). We
also found a strong correlation between the isotopic dependence of the neutron
skin thickness and the pygmy dipole strength. The fraction of the energy
weighted strength exhausted by the PDR and the neutron skin thickness show a
linear correlation with the universal rate of about 0.2/fm.
