paper

Di-neutron correlation and soft dipole excitation in medium mass neutron-rich nuclei near drip-line

arXiv:nucl-th/0408052 · doi:10.1103/PhysRevC.71.064326

Abstract

The neutron pairing correlation and the soft dipole excitation in medium-mass nuclei near drip-line are investigated from a viewpoint of the di-neutron correlation. Numerical analyses by means of the coordinate-space HFB and the continuum QRPA methods are performed for even-even O, Ca and Ni. A clear signature of the di-neutron correlation is found in the HFB ground state; two neutrons are correlated at short relative distances $\lesim 2$ fm with large probability . The soft dipole excitation is influenced strongly by the neutron pairing correlation, and it accompanies a large transition density for pair motion of neutrons. This behavior originates from a coherent superposition of two-quasiparticle configurations consisting of continuum states with high orbital angular momenta reaching an order of . It raises a picture that the soft dipole excitation under the influence of neutron pairing is characterized by motion of di-neutron in the nuclear exterior against the remaining subsystem. Sensitivity to the density dependence of effective pair force is discussed.

35 pages, 22 figures

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