Transient magnetic fields for large Z atoms recoiling through gadolinium

The g-factors of a large class of collective nuclear states are presently of considerable interest because they depend on how the total angular momenta are composed of collective and single-particle contributions. The authors have utilized Coulomb excitation of the 5-/2 first excited state in 207Pb whose g-factor is well known, to calibrate the transient field (TF) for Z = 82 recoils in ferromagnetic Gd at 77 K over a wide range of velocities, 2.4 v0 less than or equal to v less than or equal to 10.2 v0 (v0 is the Bohr velocity c/α/). At Chalk River 58Ni beams of 222 and 230 MeV were used, and at LBL a 610 MeV 136Xe beam from the SuperHILAC was used. These beams bombarded triple-layered foils, consisting of a approx.1 mg/cm2 thick target layer (97% enriched 207Pb, natural Th or U) evaporated onto rolled and annealed Gd, and an approx.12 mg/cm2 thick Cu layer evaporated onto the back of the Gd. Intimate mechanical contact of the Cu backing with a 0.8 mm thick, liquid-N2 cooled Cu plate resulted in target temperatures of approx. 80 K, well below the Curie temperature for Gd (293 K)