Surface and Volume Symmetry Energy Coefficients of a Neutron-Rich Nucleus

Using an isobaric method,the symmetry-energy coefficient(asym)of a neutron-rich nucleus is obtained from experimental binding energies.The shell effects are shown in a^(*)_(sym)/A≡4asym/A of nuclei.A(sub)magic neutron magic number N=40 is suggested in a very neutron-rich nucleus,and a^(*)_(sym)/A of a nucleus is found to decrease when its mass increases.The a^(*)_(sym)/A of a very neutron-rich nucleus with large mass saturates.The volume-symmetry coefficients(b_(v))and surface-symmetry coefficients(b_(s))of a neutron-rich nucleus are extracted from a sym*/A by a correlation a^(*)_(sym)/A=bv/A-b s/A^(4/3).It is found that bv and bs decrease when the nucleus becomes more neutron-rich,and tend to saturate in the very neutron-rich nucleus.A linear correlation between b v and bs is obtained in nuclei with different neutron-excess I,and bv of I>7 nuclei is found to coincide with the results of infinite nuclear matter a sym=32±4 MeV,and bs/bv of the nucleus is found to coincide with the results of the finite-range liquid-drop model results.