Interplay between isoscalar and isovector correlations in neutron-rich nuclei

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The interplay between isoscalar and isovector correlations in the 1⁻ states in neutron-rich (N) even-even nuclei is studied, taking examples of the nuclei, ²²₈O₁₄ and ²⁴₈O₁₆. The excitation modes explored are isovector dipole and isoscalar compression dipole modes. The self-consistent Hartree-Fock plus the random-phase approximation with the Skyrme interaction, SLy4, is solved in coordinate space so as to take properly into account the continuum effect. The isovector peak induced by isoscalar correlation, the isoscalar peak induced by isovector correlation, and the possible collective states made by both isoscalar and isovector correlations, ("iS-iV pigmy resonance"), are shown. The strong neutron-proton interaction in nuclei can be responsible for controlling the isospin structure of normal modes. It is explicitly shown that in the scattering by isoscalar (isovector) particles on N even-even nuclei isovector (isoscalar) strength in addition to isoscalar (isovector) strength may be populated.