Soft spin dipole giant resonances in 40Ca

TL;DR

This paper reports high-resolution experimental data on charge exchange reactions in calcium isotopes, revealing the first measurement of relative spin dipole strength and suggesting a vibrational band linked to pairing vibrations.

Contribution

It provides the first analysis of relative spin dipole strength in calcium isotopes and identifies a vibrational band related to pairing vibrations in 40Sc.

Findings

First measurement of relative spin dipole strength in calcium isotopes.

Identification of a vibrational band at 1.8 MeV in 40Sc.

Observation of periodic features in spin-dipole strength distribution.

Abstract

High resolution experimental data has been obtained for the 40,42,44,48Ca(3He,t)Sc charge exchange reaction at 420 MeV beam energy, which favors the spin-isospin excitations. The measured angular distributions were analyzed for each state separately, and the relative spin dipole strength has been extracted for the first time. The low-lying spin-dipole strength distribution in 40Sc shows some interesting periodic gross feature. It resembles to a soft, dumped multi-phonon vibrational band with $\hbar\omega$= 1.8 MeV, which might be associated to pairing vibrations around $^{40}$Ca.