Measurement of cross sections for α-induced reactions onAu197and thick-target yields for the(α,γ)process onZn64andCu63

Abstract

We have measured the cross sections for the $^{197}\mathrm{Au}$($\ensuremath{\alpha},\ensuremath{\gamma}$)$^{201}\mathrm{Tl}$ and $^{197}\mathrm{Au}$($\ensuremath{\alpha},2n$)$^{199}\mathrm{Tl}$ reactions in the 17.9- to 23.9-MeV energy range, and $^{197}\mathrm{Au}$($\ensuremath{\alpha},n$)$^{200}\mathrm{Tl}$ reaction in the 13.4- to 23.9-MeV energy range using an activation technique. Thick-target yields for the $^{64}\mathrm{Zn}$($\ensuremath{\alpha},\ensuremath{\gamma}$)$^{68}\mathrm{Ge}$ (7- to 14-MeV) and $^{63}\mathrm{Cu}$($\ensuremath{\alpha},\ensuremath{\gamma}$)$^{67}\mathrm{Ga}$ (7-MeV) reactions were measured. For all measurements, natural elements were bombarded with He${}^{+}$ beams from the 88 In. Cyclotron at the Lawrence Berkeley National Laboratory (LBNL). Irradiated samples were counted using a \ensuremath{\gamma}-spectrometry system at LBNL's Low Background Facility. Measured $^{197}\mathrm{Au}$($\ensuremath{\alpha},\ensuremath{\gamma}$)$^{201}\mathrm{Tl}$ cross sections were compared with the NON-SMOKER theoretical values. The thick-target yields for the $^{64}\mathrm{Zn}$($\ensuremath{\alpha},\ensuremath{\gamma}$)$^{68}\mathrm{Ge}$ and $^{63}\mathrm{Cu}$($\ensuremath{\alpha},\ensuremath{\gamma}$)$^{67}\mathrm{Ga}$ reactions are also compared with the theoretical yield, calculated numerically using the energy dependent NON-SMOKER cross section data. In both cases, measured values are found to follow a trend of overlapping the predicted value near the alpha nucleus barrier height and fall below with a slowly widening difference between them in the sub-barrier energy points.