Abstract
The E 1 strength distributions in even-even Si isotopes were calculated in the “particle-core coupling” version of the shell model taking into account the fragmentation of the hole configuration among the states of the daughter nuclei. The comparison of calculated strength distributions in different isotopes of the same element shows the peculiarities of a neutron surface influence on the E 1 resonance fragmentation.
Highlights
The problem of theoretical description of the excited states of light nuclei has been discussed for many years
From comparison of the experimental photo-excitation cross sections it is seen that a consistent increase in the number of neutrons in the isotopic chain changes drastically the resonance structure
Theoretical description of dipole resonances in some even isotopes of Ti and Ca was performed in the previous paper [2]
Summary
The increasing amount of experimental data on structure of multipole giant resonances (GR) in the cross sections of nuclear reactions has shown that microscopic approach considering only particle-hole configurations cannot reproduce a complicated structure of GR. One of the possible ways to build a set of basic configurations which could be used as doorway states in the microscopic description of nuclear resonances is to take into account the distributions of the “hole” configurations among the states with total momentum J, excitation energy E and isospin T (JET )A−1 of residual nuclei with mass number (A − 1). In the Particle Core Coupling version of Shell Model (PCC SM) these distributions are taken into account in microscopic description of multipole resonances (MR) [3, 4]. In Eq (4), α f are the results of the Hamiltonian diagonalization
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