Study of theγdecay of high-lying states in208Pb via inelastic scattering of 17O ions

F C L Crespi ,C A Ur ,V Vandone ,Ana Isabel Morales ,B Birkenbach ,M Bellato ,L Pellegri ,R Nicolini ,B Siebeck ,G Benzoni ,J Grębosz ,K Mazurek ,S Siem ,S Brambilla ,G De Angelis ,M Krzysiek ,F Recchia ,Enrico Calore ,A Görgen ,O Wieland ,A Gottardo ,C Boiano ,D Mengoni ,S Leoni ,D Bortolato ,S Ceruti ,M Kmiecik ,F Camera ,A Bracco ,S Riboldi ,M Ciemała ,A Maj ,M Ziębliński ,S Lunardi ,S M Lenzi ,S Bottoni ,E Farnea ,P Molini ,N Blasi ,A Giaz ,D R Napoli ,D Bazzacco ,C Michelagnoli ,E Šahin ,B Million ,P Bednarczyk ,A Gadea ,R Isocrate ,J J Valiente Dobón

doi:10.1051/epjconf/20146602023

Abstract

A measurement of the high-lying states in 208Pb has been made using 17O beams at 20 MeV/u. The gamma decay following inelastic excitation was measured with the detector system AGATA Demonstrator based on segmented HPGe detectors, coupled to an array of large volume LaBr3:Ce scintillators and to an array of Si detectors. Preliminary results in comparison with (γ,γ’) data, for states in the 5-8 MeV energy interval, are presented.

Highlights

The giant dipole resonance (GDR), a collective oscillation of the protons against the neutrons, dominates the electric dipole response of nuclei
An example of a twodimensional histogram displaying the Total Kinetic Energy (TKE) of 17O ions measured in one pad of the ΔE-E silicon telescopes versus the energy deposit measured in the ΔE pad is shown in the right panel of Figure 1
We considered for each event the angle (,recoil) between the gamma-ray emission direction and the 208Pb recoil velocity vector

Summary

Introduction

The giant dipole resonance (GDR), a collective oscillation of the protons against the neutrons, dominates the electric dipole response of nuclei. [2-9]) performed with stable and unstable neutron rich nuclei evidenced the presence of an accumulation of electric dipole strength at energies around the particle threshold, larger than that due to the low energy tail of the GDR This is commonly denoted as the Pygmy Dipole Resonance Experiments performed with different probes are found to be complementary, altering the relative population of the different states, in particular it is interesting to study PDR states using a probe interacting mainly at the surface of the nucleus. In this contribution an experiment to study the gamma decay of E1 states (in the PDR region) via inelastic scattering of 17O ions accelerated at 20 MeV/u [15] is described and some preliminary results discussed

Experimental technique and setup

Preliminary results

Conclusions