Difference between stable and exotic nuclei: medium polarization effects

TL;DR

This paper investigates the role of medium polarization effects, specifically phonon exchange, in nuclear pairing, providing evidence from reactions involving exotic halo nuclei like 11Li.

Contribution

It demonstrates that phonon-mediated pairing significantly contributes to nuclear pairing gaps, especially in highly polarizable exotic nuclei like 11Li.

Findings

Evidence of phonon-mediated pairing from 11Li+p reaction

Medium polarization effects influence pairing in exotic nuclei

Reactions with halo nuclei reveal collective vibration contributions

Abstract

The bare NN-potential, parametrized so as to reproduce the nuclear phase shifts leads to a sizable Cooper pair binding energy in nuclei along the stability valley. It is a much debated matter whether this value accounts for the "empirical" value of the pairing gap or whether a similarly important contribution arises from the exchange of collective vibrations between Cooper pair partners. In keeping with the fact that two-particle transfer reactions are the specific probe of pairing in nuclei, and that exotic halo nuclei like 11Li are extremely polarizable, we find that the recent studied reaction, namely 11Li+p -> 9Li+t, provides direct evidence of phonon mediated pairing in nuclei.