Excitation function measurement of ${}^{144}$Sm($\alpha$,n) reaction at sub-Coulomb energies and detailed covariance analysis

The cross-section measurement of ${}^{144}$Sm($\alpha$,n)${}^{147}$Gd (T${}_{1\mathrm{/}2}=$38.06(12) h) reaction has been performed at sub-Coulomb energies around 14$-$21 MeV ($V_{coul}\approx 21.8$ MeV) using the stacked foil activation technique. Irradiated targets were prepared from enriched (67%) ${}^{144}$Sm${}_2$O${}_3$ powder using molecular deposition technique between thickness 280$-$350 $\mu$g/cm${}^2$ on high purity Al backing. A detailed simulation has been carried out to address the energy uncertainty in the irradiated beam energy followed by a comprehensive discussion of various uncertainties in the form of covariance and correlation matrices. Finally the excitation functions are compared with the previously measured experimental data from literature and the theoretical predictions obtained using Hauser-Feshbach statistical model code.