PROTON EMISSION IN INELASTIC-SCATTERING OF CA-40 ON CA-40 AT 50 MEV NUCLEON/

Inelastic scattering of Ca-40 on Ca-40 at 50 MeV/nucleon has been meas ured in coincidence with Light charged particles detected over a large angular domain. The giant resonance region of the inelastic spectrum is shown to be dominated by the isoscalar giant quadrupole resonance. The characteristics of the emitted protons allow us to separate four r eaction mechanisms contributing to the high excitation energy region o f the inelastic spectrum (E > 30 MeV): pickup breakup, knockout, inel astic scattering to high-lying target states, and a new mechanism resp onsible for the emission of fast-moving protons. A sizable direct deca y branch towards hole states of K-39 is measured for the giant quadrup ole resonance in Ca-40. Evidence is given for the excitation of the tw o-phonon giant quadrupole resonance, characterized by its direct decay scheme. The energy and width of this two-phonon state are in agreemen t with a harmonic picture for collective nuclear excitations.