Evolution of magnetic dipole strength in Sn100−140 isotope chain and the quenching of nucleon g factors

Abstract

The evolution of electromagnetic transitions along isotope chains is of particular importance for the nuclear structure and dynamics, as well as for the r-process nucleosynthesis. Recent measurement of inelastic proton scattering on even-even 112−124 Sn isotopes provides a novel insight into the isotopic dependence of E1 and M1 strength distributions. We investigate M1 transitions in eveneven 100−140 Sn isotopes from a theoretical perspective, based on relativistic nuclear energy density functional. The M1 transition strength distribution is characterized by an interplay between single and double-peak structures, that can be understood from the evolution of single-particle states, their occupations governed by the pairing correlations, and two-quasiparticle transitions involved. It is shown that discrepancy between model calculations and experiment on B(M1) transition strength is considerably reduced than previously known, and the quenching of the g-factors for the free nucleons needed to reproduce the experimental data on M1 transition strength amounts g ef f /g f ree =0.80-0.93. Since some of the B(M1) strength above the neutron threshold may be missing in the inelastic proton scattering measurement, further experimental studies are required to confirm if only small modifications of the bare g-factors are actually needed when applied in finite nuclei.

Magnetic quadrupole transitions in the relativistic energy density functional theory

“…Theory framework employed in this work follows the formalism based on relativistic energy density functional recently developed in studies of M1 transitions [44][45][46][47][48]. The nuclear ground state represents the basis for studies of excitations, and it is described by employing selfconsistent RHB model as given in Ref.…”

Electric dipole transitions in the relativistic quasiparticle random-phase approximation at finite temperature

“…Numerous theoretical and experimental investigations have been conducted to explore the isotopic sensitivity of both natural parity electric dipole (E 1) and unnatural parity magnetic dipole (M1) responses. These studies revealed a pronounced dependence of dipole strength distributions on the neutronto-proton (N/Z) ratio [21][22][23][24][25][26][27][28][29][30]. Given that nuclei can also exist in extreme conditions within stellar environments, there has been a growing interest in understanding the temperature dependence of nuclear excitations.…”