Effekte hoeherer Ordnung in der elektromagnetischen Dissoziation schwach gebundener Kerne

The present work deals with the dissociation mechanisms of loosely bound nuclei in heavy ion collisions, a subject which is closely related to current experiments at heavy ion colliders (RIKEN, GSI, GANIL, MSU-NSCL etc.). Out study is based on the available data on the photodissociation of "1"1Be, "9Be, "1"1Li, and the neutron capture by "1"2C. Generalising the effective range treatment of photo-nuclear reactions near threshold to describe reactions involving also bound states with a non-zero angular momentum, we derive general expressions for electromagnetic and diffraction dissociation matrix elements and cross-sections, which appear in good approximation to be independent of any assumption on the shape of the nuclear interaction. We have also calculated the mean square distance of loosely bound clusters to the core. Corrections can be worked out in a systematic way. Our mainly analytical calculations are in good agreement with the experimental data and with the previously available numerical results. We have studied the effects of higher order electromagnetic interactions in the Coulomb dissociation of "1"1Li and "9Be in the sudden approximation and we have found a trend to the reduction of the dissociation probability. Higher order effects introduce also an asymmetry in the angular distribution of the emitted particles. We have finally studied the time evolution of the final state wave function after a Coulomb dissociation. (orig.)SIGLEAvailable from TIB Hannover: RA 831(3168) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman