Discontinuity in the Transient Magnetic Field aroundZ1=9andZ2=26

$K$-vacancy fractions have been measured for O ions moving in Fe and for F ions moving in Fe, Co, and Ni at velocities $2.1<~\frac{v}{v_0}<~10.5$. Discontinuities that explain those found for the transient magnetic field are observed. The present findings indicate that (i) the transient field cannot be approximated by a linear velocity dependence for $Z_1<~8$ in Fe and for $Z_1<~9$ in Co and Ni, and (ii) the discontinuity in the transient field is only present at velocities below $4v_0$.