Electric and magnetic dipole strength in Zn66

R Schwengner,W Tornow,A Frotscher,S Johnson,J Sinclair,R V F Janssens,O Wieland,J Kleemann,S Urlaß,Krishichayan Krishichayan,O Papst,N Benouaret,F Ludwig,M Scheck,A Wagner,R Massarczyk,S Turkat,F Fiedler,E Hoemann,U Friman-Gayer,A R Junghans,M P Takács,E Pirovano,C Fransen,R Beyer,V Werner,J Wilhelmy,T Beck,D Bemmerer,Sean Finch ,Thomas Hensel ,Giorgio Battaglia ,R González ,David Little ,D O’donnell ,Maik Butterling ,S Müller ,Hans Hoffmann ,Andreas Hartmann ,Nicola Kelly ,Michael D Jones ,Michael Grieger

doi:10.1103/physrevc.103.024312

Abstract

The dipole strength of the $N=28$ closed-shell nuclide $^{54}\mathrm{Fe}$ was studied in photon-scattering experiments using bremsstrahlung produced with electron beams of kinetic energies of 7.5 and 13.9 MeV at the $\ensuremath{\gamma}\mathrm{ELBE}$ facility as well as using quasimonoenergetic and linearly polarized photon beams of 26 different energies within the range from 5.5 to 11.4 MeV at the $\mathrm{HI}\ensuremath{\gamma}\mathrm{S}$ facility. About 100 $J=1$ states were newly identified, out of them 19 with ${1}^{+}$ and 30 with ${1}^{\ensuremath{-}}$ assignments. The quasicontinuum of unresolved transitions was included in the analysis of the spectra and the intensities of branching transitions were estimated on the basis of simulations of statistical $\ensuremath{\gamma}$-ray cascades. As a result, the photoabsorption cross section up to the neutron-separation energy was determined and compared with predictions of the statistical reaction model. The experimental $M1$ strengths from resolved ${1}^{+}$ states are compared with results of large-scale shell-model calculations.

Highlights

Experimental and theoretical studies of photon strength functions have attracted growing interest in the past years [1,2]
The dipole strength of the nuclide 66Zn was studied in photon-scattering experiments using bremsstrahlung produced with electron beams of energies of 7.5 and 13.4 MeV at the γ ELBE facility as well as using quasimonoenergetic and linearly polarized photon beams of 30 energies within the range of 4.3 to 9.9 MeV at the high-intensity γ -ray source (HIγ S) facility
The present (γ, γ ) cross section shows pronounced extra strength above the three Lorentz functions (TLO) in the energy region from about 6 MeV to Sn, which is attributed to the pygmy dipole resonance (PDR)

Summary

Introduction

Experimental and theoretical studies of photon strength functions have attracted growing interest in the past years [1,2]. These functions describe average transition strengths in the energy region of the quasicontinuum of nuclear levels and are important ingredients for calculations of reaction cross sections within the statistical reaction model [3]. Such calculations are used, for example, to obtain information about radiative neutron-capture cross sections of unstable nuclides.

Results

Discussion

Conclusion