Electric monopole transitions inCa40

The $E0\mathrm{}$ pair decay branching ratio ($\frac{{\Gamma }_{\pi }}{\Gamma }$) for the 5.21-MeV $0^{+}$ fifth excited state of ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ was measured. The state was excited by inelastic proton scattering. The $e^{-}-e^{+}$ pairs were detected in two $\Delta E-E$ scintillation telescopes in coincidence with backscattered protons. A branching ratio limit of 1.4×${10}^{-3\mathrm{}}$ was determined which corresponds to a monopole strength $\rho <0.06\mathrm{}$. This result is consistent with theoretical descriptions which contain multiparticle excitations and core deformations. In addition, the branching ratio $R\left(\frac{(2_2^{+}\to 0_2^{+})}{(2_2^{+}\to 0_1^{+})}\right)=(2.1\mathrm{}\pm 0.1)\times {10}^{-2\mathrm{}}$ for the decay of 5.25-MeV $2^{+}$ state was measured and corresponds to a $B\left(E2\mathrm{}\right)=(3.5\mathrm{}\pm 0.6) e^2$ ${\mathrm{fm}}^4$.