Measurements of theCu63(γ, n)and (γ, 2n) Cross Sections

Abstract

The $^{63}\mathrm{Cu}(\ensuremath{\gamma}, n)$ cross section was measured over the energy range from threshold to 25 MeV with a photon beam of 2.0% resolution which was produced by the inflight annihilation of positrons. The ($\ensuremath{\gamma}, n$) cross section was found to have a maximum value of 75\ifmmode\pm\else\textpm\fi{}6 mb at about 17.1 MeV and an integrated value up to 25 MeV of 490\ifmmode\pm\else\textpm\fi{}40 MeV mb. No structure was observed in these measurements or in additional ($\ensuremath{\gamma}, n$) measurements which were made in the region of the peak of the giant resonance with 1.5% $\ensuremath{\gamma}$-ray resolution. The ($\ensuremath{\gamma}, n$) data from the present experiment were combined with the $(\ensuremath{\gamma}, n)+(\ensuremath{\gamma}, pn)$ data from Livermore to obtain the $^{63}\mathrm{Cu}(\ensuremath{\gamma}, pn)$ cross section, which was found to have a maximum value of 15\ifmmode\pm\else\textpm\fi{}4 mb at about 23 MeV and an integrated value up to 25 MeV of 60\ifmmode\pm\else\textpm\fi{}15 MeV mb. In addition, the $^{63}\mathrm{Cu}(\ensuremath{\gamma}, 2n)$ cross section was measured at three representative energies between threshold and 26 MeV. The maximum ($\ensuremath{\gamma}, 2n$) cross section obtained was 10.0\ifmmode\pm\else\textpm\fi{}1.6 mb at 23.7 MeV. The results of the experiments are compared with previous measurements and with theory. A small bump in the $(\ensuremath{\gamma}, n)+(\ensuremath{\gamma}, pn)+(\ensuremath{\gamma}, 2n)$ cross section at about 23 MeV may possibly be attributed to an analog giant resonance.