Measurements of Dipole Excitations in $^{48}$Ca Between E$_{\gamma}$ = 9.5 and 15.3 MeV

ORAL

Abstract

$^{48}$Ca photodisintegration cross sections were measured using $\gamma$-ray beams of 34 different energies between 9.5 and 15.3 MeV generated with the TUNL High-Intensity $\gamma$-ray Source (HI$\gamma$S). The cross sections were measured with a 2.7 g $^{48}$Ca target enriched to 92\% using an array of $^{3}$He proportional-counters embedded in thermalizing polyethylene. The absolute cross sections for the $^{48}$Ca($\gamma$,n) reaction were obtained by normalization to the well known $^{2}$H($\gamma$,n) reaction cross sections. Single neutron emission is the dominant channel in this energy range and its detection provides a measurement of dipole excitation strength such as the previously identified M1 strength at E$_{\gamma}$ = 10.22 MeV,\footnote{W.Steffen \textit{et al.} Nucl. Phys. A \textbf{404}, 413 (1983).} for which a new value will be presented. Structures on the low-energy tail of the E1 GDR were also observed and will be presented.

*This work was supported in part by USDOE Grant Nos. DE-FG02-97ER41041, DE-FG02-03ER41231, DE-FG02-87ER-40316, and DHS Grant No. 2008-DN-077-ARI010-0.

Authors

  • J.R. Tompkins

    • UNC Chapel Hill, TUNL
    • UNC-Chapel Hill and TUNL
  • C.W. Arnold

    • UNC-Chapel Hill and TUNL
  • H.J. Karwowski

    • UNC-Chapel Hill and TUNL
  • G.C. Rich

    • UNC-Chapel Hill and TUNL
  • C.R. Howell

    • Duke University, TUNL
    • Duke University and Triangle Universities Nuclear Laboratory (TUNL)
    • Duke University and TUNL
  • L.G. Sobotka

    • Washington University in St. Louis