# Influence of complex configurations on properties of pygmy dipole resonance in neutron-rich Ca isotopes

## TL;DR

This study investigates how phonon-phonon coupling influences the low-energy electric dipole response in neutron-rich calcium isotopes using a quasiparticle random phase approximation with Skyrme interaction, providing new predictions for isotopes beyond current experimental data.

## Contribution

It introduces the effects of phonon-phonon coupling into the quasiparticle random phase approximation for calcium isotopes, offering new insights and predictions for neutron-rich nuclei.

## Key findings

- PPC causes formation of low-energy 1- states.
- PPC affects low-energy E1 strength in certain isotopes.
- Predicted increase in E1 strength below 10 MeV with neutron number.

## Abstract

Starting from the quasiparticle random phase approximation based on the Skyrme interaction SLy5, we study the effects of phonon-phonon coupling~(PPC) on the low-energy electric dipole response in $^{40-58}$Ca. Using the same set of parameters we describe available experimental data for $^{40,44,48}$Ca and give prediction for $^{50-58}$Ca. The inclusion of the PPC results in the formation of low-energy $1^-$ states. There is an impact of the PPC effect on low-energy $E1$~strength of $^{40,44,48}$Ca. The PPC effect on the electric dipole polarizability is discussed. We predict a strong increase of the summed $E1$~strength below 10MeV, with increasing neutron number from $^{48}$Ca till $^{58}$Ca.