Projectile Coulomb excitation with fast radioactive beams

Search for γ rays emanating from Coulomb excitation of fast (30-46 MeV/u) radioactive projectiles 8He, 11,12,14Be interacting with a lead target is reported. They are clearly identified by their Doppler shift. The 320 keV 1/2- -> 1/2+ γ transition from 11Be was observed with a cross-section of 191 ± 26 mb which is noticeably less than expected from the known lifetime and in the perturbation limit of pure Coulomb excitation. In the other nuclei rather stringent upper limits of 0.01 to 0.2 Weisskopf units are placed on the hypothetical transition to 1- states. (author)