Interplay between single-particle and collective excitations in argon isotopes populated by transfer reactions

Abstract

New $\ensuremath{\gamma}$ transitions have been identified in argon isotopes in ${}^{40}$Ar + ${}^{208}$Pb multiple transfer reactions by exploiting, in a fragment-$\ensuremath{\gamma}$ measurement, the new generation of magnetic spectrometers based on trajectory reconstruction coupled to large $\ensuremath{\gamma}$ arrays. The coupling of single-particle degrees of freedom to nuclear vibration quanta was discussed. The interpretation of the newly observed states within a particle-phonon coupling picture was used to consistently follow, via their excitation energies, the evolution of collectivity in odd Ar isotopes. The proposed level schemes are supported by the results of $sd$-$pf$ shell-model calculations, which have been also employed to evaluate the strength functions of the populated states.