Velocity dependence of the transient hyperfine field at Pd ions swiftly recoiling through magnetized Fe

The velocity dependence of the transient hyperfine magnetic field manifest at nuclei of ${}_{}{}^{108}{}_{}{}^{}\mathrm{Pd}$ ions recoiling through magnetized Fe was investigated to a velocity higher than previously examined for the heavier nuclides. The state of interest ($2_1^{+}$) was populated by Coulomb excitation using beams of 80-MeV ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ and 180-MeV ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ ions and precessed $\gamma$-ray angular distribution measurements were carried out in coincidence with backscattered projectiles. These results, when combined with prior lower-velocity measurements for ${}_{}{}^{106}{}_{}{}^{}\mathrm{Pd}$, yield a transient field velocity dependence $v^p$, $p=0.41\mathrm{}\pm 0.15$, for Pd isotopes over the extended velocity range $1.74\le 〈\frac{v}{v_0}〉\le 7.02 (v_0=\frac{c}{137})$ a result incompatible with a linear velocity dependence.