Wavelet signatures of K-splitting of the Isoscalar Giant Quadrupole Resonance in deformed nuclei from high-resolution (p,p′) scattering off 146, 148, 150Nd

C O Kureba ,J Mabiala,P Papka,J Carter,A Krugmann,J Kvasil,G.R.J Cooper,Z Buthelezi,A Richter,P Von Neumann-Cosel,W Kleinig,A Tamii,R Neveling,M Jingo,G Steyn ,J P Mira ,A M Krumbolz ,J A Swartz ,F D Smit ,S V Förtsch ,V O Nesterenko ,P.‐G Reinhard ,E Sideras‐Haddad ,R Fearick ,I T Usman

doi:10.1016/j.physletb.2018.02.013

Abstract

The phenomenon of fine structure of the Isoscalar Giant Quadrupole Resonance (ISGQR) has been studied with high energy-resolution proton inelastic scattering at iThemba LABS in the chain of stable even-mass Nd isotopes covering the transition from spherical to deformed ground states. A wavelet analysis of the background-subtracted spectra in the deformed 146, 148, 150Nd isotopes reveals characteristic scales in correspondence with scales obtained from a Skyrme RPA calculation using the SVmas10 parameterization. A semblance analysis shows that these scales arise from the energy shift between the main fragments of the K=0,1 and K=2 components.

Highlights

Nuclear giant resonances are a prime example of elementary excitation modes and important sources of information about nuclear collectivity
Our previous survey of fine structure of the Isoscalar Giant Quadrupole Resonance (ISGQR) established coupling to lowlying phonons as a major source of wavelet scales in spherical/vibrational nuclei [3, 4], while the present manuscript has a focus on the role of ground state deformation
The observation of fine structure in heavy deformed nuclei is far from trivial considering the extremely high level densities of 2+ states in the corresponding excitation energy region (107 − 108 MeV−1 estimated from Refs. [38, 39])

Summary

Introduction

Nuclear giant resonances are a prime example of elementary excitation modes and important sources of information about nuclear collectivity. A systematic experimental investigation of the fine structure of the Isoscalar Giant Quadrupole Resonance (ISGQR) at different shell closures over a wide mass range with high-resolution proton inelastic scattering experiments was conducted at the K600 magnetic spectrometer of iThemba LABS [3,4,5] These studies showed that in medium-mass to heavy nuclei, experimentally observed energy scales quantitatively characterizing the fine structure could be related to those extracted from microscopic calculations involving coupling of the initial collective one. [20] exhibit, a broadening of the Lorentzian shape with increasing ground-state deformation, and a transition from a single Lorentzian shape in the semimagic 142Nd two a double-Lorentzian structure in the most deformed nucleus 150Nd ( the latter is called into question by recent results [21]) No such effect has been seen in inelastic alpha scattering studies of the ISGQR in the Nd [22] or the analog Sm [23] isotope chains. Our previous survey of fine structure of the ISGQR established coupling to lowlying phonons as a major source of wavelet scales in spherical/vibrational nuclei [3, 4], while the present manuscript has a focus on the role of ground state deformation

Experiment

Theoretical model calculations

Wavelet signature for K-splitting from a semblance analysis

Conclusions