Pygmy Quadrupole Resonance in Skin Nuclei

TL;DR

This paper explores the theoretical electric quadrupole response in tin isotopes, revealing a new Pygmy Quadrupole Resonance mode linked to neutron skin oscillations, expanding understanding of nuclear skin phenomena.

Contribution

It introduces the concept of Pygmy Quadrupole Resonances (PQR) as a new mode related to neutron skin oscillations, based on HFB and QPM calculations.

Findings

Identification of PQR states linked to neutron excess

Spectral distributions show clustering of additional strength

Transition densities suggest skin-core oscillation

Abstract

The electric quadrupole response is investigated theoretically by HFB and QPM calculations along the Sn isotopic chain with special emphasis on excitations above the first collective state and below the particle threshold. Depending on the asymmetry, additional strength clustering as a group of states similar to the known PDR mode is found. The spectral distributions and electric response functions are discussed. The transition densities of these Pygmy Quadrupole Resonances (PQR) states are closely related to the neutron excess and showing special features being compatible with an oscillation of the neutron skin against the nuclear core. These features may indicate a new nuclear quadrupole mode connected to the skin configuration.