Electromagnetic dissociation for high- Z projectiles and at ultrarelativistic energies

Experiments to determine the characteristics of electromagnetic dissociation (ED) has been extended to high projectile charge and ultrarelativistic energies using ¹³⁹La and ¹⁶O projectiles on ¹⁹⁷Au targets. The gross features are reproduced in a Weizs\"acker-Williams calculation but significant systematic deviations appear. The results are used as a guide in extending the calculations to the regime of energies and projectiles expected for planned heavy-ion colliders where Ed effects should comprise a major fraction of the total cross section.