Electric monopole transitions in 40Ca

The E0 pair decay branching ratio (GAMMA/sub π//GAMMA) for the 5.21-MeV 0+ fifth excited state of 40Ca was measured. The state was excited by inelastic proton scattering. The e--e+ pairs were detected in two ΔE-E scintillation telescopes in coincidence with backscattered protons. A branching ratio limit of 1.4 x 10-3 was determined which corresponds to a monopole strength rho < 0.06. This result is consistent with theoretical descriptions which contain multiparticle excitations and core deformations. In addition, the branching ratio R ((2+2 → 0+2)/(2+2 → 0+1)) = (2.1 +- 0.1) x 10-2 for the decay of 5.25-MeV 2+ state was measured and corresponds to a B (E2) = (3.5 +- 0.6) e2 fm4