Nuclear electromagnetic dipole response with the Self-Consistent Green's Function formalism

Abstract

Microscopic calculations of the electromagnetic response of medium-mass nuclei are now feasible thanks to the availability of realistic nuclear interactions with accurate saturation and spectroscopic properties, and the development of large-scale computing methods for many-body physics. The purpose is to compute isovector dipole electromagnetic (E1) response and related quantities, i.e. integrated dipole cross section and polarizability, and compare with data from photoabsorption and Coulomb excitation experiments. The single-particle propagator is obtained by solving the Dyson equation, where the self-energy includes correlations non-perturbatively through the Algebraic Diagrammatic Construction (ADC) method. The particle-hole ($ph$) polarization propagator is treated in the Dressed Random Phase Approximation (DRPA), based on an effective correlated propagator that includes some $2p2h$ effects but keeps the same computation scaling as the standard Hartree-Fock propagator. The E1 responses for ${}^{14,16,22,24}$O, ${}^{36,40,48,52,54,70}$Ca and ${}^{68}$Ni have been computed: the presence of a soft dipole mode of excitation for neutron-rich nuclei is found, and there is a fair reproduction of the low-energy part of the experimental excitation spectrum. This is reflected in a good agreement with the empirical dipole polarizability values. For a realistic interaction with an accurate reproduction of masses and radii up to medium-mass nuclei, the Self-Consistent Green's Function method provides a good description of the E1 response, especially in the part of the excitation spectrum below the Giant Dipole Resonance. The dipole polarizability is largely independent from the strategy of mapping the dressed propagator to a simplified one that is computationally manageable

14 pages, 12 figures

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Cited by in corpus (24)

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• Nuclear Charge Radii of the Nickel Isotopes ${}^{58-68,70}$Ni
• Improved many-body expansions from eigenvector continuation
• Charge radius of the short-lived ${}^{68}$Ni and correlation with the dipole polarizability
• Equation of Motion Method to strongly correlated Fermi systems and Extended RPA approaches
• Normal-ordered $k$-body approximation in particle-number-breaking theories
• Testing ab initio nuclear structure in neutron-rich nuclei: lifetime measurements of second 2+ states in 16C and 20O
• Zero- and finite-temperature electromagnetic strength distributions in closed- and open-shell nuclei from first principles
• Gorkov algebraic diagrammatic construction formalism at third order
• Electromagnetic observables of open-shell nuclei from coupled-cluster theory
• Diagrammatic ab initio methods for infinite nuclear matter with modern chiral interactions
• Investigation of the ground-state spin inversion in the neutron-rich 47,49Cl isotopes
• Core-polarization effects and effective charges in O and Ni isotopes from chiral interactions
• Importance truncation in non-perturbative many-body techniques
• Structure and dynamics of open-shell nuclei from spherical coupled-cluster theory
• Nuclear multipole responses from chiral effective field theory interaction
• Computing nuclear response functions with time-dependent coupled-cluster theory
• Theory of nuclear collective vibrations
• Nambu-Covariant Many-Body Theory II: Self-Consistent Approximations
• Ab initio calculations of monopole sum rules: From finite nuclei to infinite nuclear matter
• Recent applications of the subtracted second RPA method
• Bulk and spectroscopic nuclear properties within an ab initio renormalized random-phase approximation framework