Excitation energy deposition in 209Bi(a,a') reactions at 240 MeV

Neutron fold distributions measured for the reaction (209)Bi(alpha,alpha') at 240 MeV have been analyzed with the help of Statistical Model calculations to determine the distribution of excitation energy in the primary target fragments as a function of the projectile energy loss, EL. Results show that the distributions in excitation energy feature a plateau which extends from the kinematical limit E(x)=EL to very small excitations, suggesting a variety of interactions of the beam particles with the target nucleus. Requiring an additional coincidence with a light charged particle leads to selection of a significant higher average excitation energy. This effect is extrapolated to explore results of previous GDR decay measurements in the case of a (208)Pb target. Corrections of derived GDR parameters due to the partial transfer of excitation energy are suggested.