Particle decay from the giant resonance region ofCa40

The reactions ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}(\alpha , 2\alpha ){}_{}{}^{36}{}_{}{}^{}\mathrm{Ar}$ and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}(\alpha , \alpha p){}_{}{}^{39}{}_{}{}^{}\mathrm{K}$ have been studied at 115-MeV bombarding energy in order to obtain the charged particle decay characteristics of the giant quadrupole resonance at $E_x=18.0\mathrm{}$ MeV. Energy and angle were measured for both outgoing light particles to completely define the kinematics. Weak proton decay to the $d_{\frac{3}{2}}$ ($\frac{{\Gamma }_{p_0}}{\Gamma }={0.08}_{-0.03\mathrm{}}^{+0.05\mathrm{}}$) and $s_{\frac{1}{2}}$ ($\frac{{\Gamma }_{p_1}}{\Gamma }={0.22}_{-0.08\mathrm{}}^{+0.05\mathrm{}}$) hole states of ${}_{}{}^{39}{}_{}{}^{}\mathrm{K}$ was observed from the giant quadrupole resonance while most of the decay proceeded to the region of the $d_{\frac{5}{2}}$ hole states. While the ($\alpha , 2\alpha$) reaction populated the ${}_{}{}^{36}{}_{}{}^{}\mathrm{Ar}$ ground state (${\mathrm{O}}^{+}$), 1.97-MeV state ($2^{+}$), and 4.18-4.44-MeV states ($4^{+}$, $3^{-}$), only upper limits could be established for α decay of the giant quadrupole resonance ($\frac{{\Gamma }_{a_0}}{\Gamma }<0.06\mathrm{}$). Significant decay of the 14-MeV $L=2\mathrm{}$ state to the ground state of ${}_{}{}^{36}{}_{}{}^{}\mathrm{Ar}$ was observed ($\frac{{\Gamma }_{a_0}}{\Gamma }\sim 0.9\pm 0.2$).