Low-energy excitations and gamma -decay branchings in ^{124}Sn via (p,p\u2019gamma ) at E_p={15},,hbox {MeV}

Michelle Färber,Andreas Zilges,Michael Weinert,Miriam Müscher,Julius Wilhelmy,Mark Spieker

doi:10.1140/epja/s10050-021-00422-x

Abstract

The dipole response of the proton-magic nucleus {}^{124}hbox {Sn} was previously investigated with electromagnetic and hadronic probes. Different responses were observed revealing the so-called isospin splitting of the Pygmy Dipole Resonance (PDR). Here we present the results of a new study of {}^{124}hbox {Sn} using inelastic proton scattering at low energies to test an additional probe possibly exciting states of the PDR. The response to the new probe as well as the gamma -decay behavior of excited states were studied. The {}^{124}hbox {Sn}(p,p’gamma ) experiment was performed at E_p = {15},,hbox {MeV} using the combined spectroscopy setup SONIC@HORUS at the Tandem accelerator of the University of Cologne. Proton-gamma coincidences were recorded, enabling a state-to-state analysis due to the excellent energy resolution for both particles and gamma rays. J=1 states in the PDR region were populated in the present inelastic proton scattering experiment. Many gamma -decay branching ratios could be determined.

Highlights

In nuclear physics, different experimental probes and techniques are utilized to investigate structure phenomena and to understand their microscopic origins
Since no angular correlations are studied in this work only excitations that were identified at the same energy as J = 1 states in nuclear resonance fluorescence (NRF) experiments [13,20,21] were analyzed in the present (p,p’γ ) experiment
The proton-magic nucleus 124Sn was investigated via inelastic proton scattering and γ spectroscopy at energies of E p = 15 MeV

Summary

Introduction

Different experimental probes and techniques are utilized to investigate structure phenomena and to understand their microscopic origins. This approach has been applied to study the low-lying electric dipole strength – often denoted as Pygmy Dipole Resonance (PDR) – in atomic nuclei during the last two decades. This excitation mode is located around and below the particle emission thresholds [1, 2]. The PDR exhausts only a marginal fraction of the isovector dipole energy-weighted sum rule in stable or mod-

Methods

Results

Conclusion