Measurement of ${\hat{I}}^3$ rays from the giant resonances excited by ${}^{12}$C$(p,p^{\prime })$ reaction at 392 MeV and 0${}^{\circ }$

Abstract

We measured both the differential cross section ($\ddot{I}{ƒ}_{p,p^{\prime }}$ $=d^2\ddot{I}ƒ/d\hat{I}\text{c◯}d{E}_x$) and the ${\hat{I}}^3$-ray emission probability ($R_{\hat{I}}^3(E_x)$ $=\ddot{I}{ƒ}_{p,p^{\prime }{\hat{I}}^3}$/$\ddot{I}{ƒ}_{p,p^{\prime }}$) from the giant resonances excited by ${}^{12}\mathrm{C}$(\textit{p,p}${}^{\prime }$) reaction at 392 MeV and 0${}^{\circ }$, using a magnetic spectrometer and an array of NaI(Tl) counters. The absolute value of $R_{\hat{I}}^3(E_x)$ was calibrated by using the well-known ${\hat{I}}^3$-ray emission probability from ${}^{12}{\mathrm{C}}^{\ast }(15.11$ MeV, $1^{+}$, $T=1$) and ${}^{16}{\mathrm{O}}^{\ast }(6.9$ MeV, $2^{+}$, $T=0$) states within 5\% uncertainty. We found that $R_{\hat{I}}^3(E_x)$ starts from zero at $E_x=16$ MeV, increases to a maximum of 53.3$\pm$0.4$\pm$3.9\% at $E_x=27$ MeV and then decreases. We also compared the measured values of $R_{\hat{I}}^3(E_x)$ with statistical model calculation based on the Hauser-Feshbach formalism in the energy region $E_x=$ 16-32 MeV and discussed the features of ${\hat{I}}^3$-ray emission probability quantitatively.

15 pages, 14 figures, Submitted to Physical Review C