The decay of isoscalar giant resonances in 24Mg and 40Ca

In this paper we present data on the charged-particle decay of the isoscalar 2+ strength between 10 and 20 MeV excitation energy (Esub(x)) in 24Mg and 40Ca. The isoscalar strength was excited by inelastic scattering of 120 MeV α-particles at 140 and 12.50 for 24Mg and 40Ca, respectively. The charged particles originating from the decay were detected in coincidence with the α' particles at several angles in the scattering plane. Jsup(π) assignments of the decaying states were made on the basis of the angular correlation pattern of the α0 decay to the ground state of 20Ne and 36Ar, respectively, using a DWBA calculation for the m-state population of the decaying state. For 40Ca, about 40% of the E2 EWSR is found to be located in the interval Esub(x)=13.5+-1.5 MeV, which is similar to what has been found from previous inelastic scattering experiments at Esub(x)=18+-2 MeV, but much more than such experiments located in the region Esub(x)=12-15 MeV. The E2 strength distribution for 40Ca obtained is very different from what previous theoretical calculations predict. For 24Mg about 30% of the E2 EWSR is present in the interval 12.5<=Esub(x)<=16.5 MeV which again is about twice as much as deduced from previous inelastic scattering experiments. (orig./HSI)