Direct evidence for enhanced transient fields on fast 56Fe ions recoiling through thin iron

Results of ion-implantation perturbed-angular-correlation measurements on 56Fe ions recoiling through magnetized Fe at high recoil energy (E/sub R/ approx. = 56 MeV) are reported. Angular shifts were measured using targets of various thicknesses for which the excited nuclei either stopped in or recoiled out of the iron. The results clearly establish the existence of enhanced transient fields acting on fast recoiling ions leaving the magnetized Fe foil and stopping in Cu. In such measurements the contributions from the static field and from the normal Lindhardt-Winther field are eliminated. The possible use of this technique for measurements of magnetic moments of short-lived states is discussed. An experiment in which the 56Fe ions recoiled into vacuum through the polarized foil was also carried out. In this case a strong attenuation of the angular correlation was observed; however, no excessive precession was seen, as would be observable if polarized hf fields persisted in vacuum for a substantial part of the nuclear lifetime