Time-differential-free hyperfine field measurement at low recoil velocities

A time-differential plunger technique has been used to observe the temporal attenuation of a $\gamma$-ray angular distribution. Nuclei of ${}_{}{}^{152}{}_{}{}^{}\mathrm{Sm}$ were Coulomb excited by 3 and 4 MeV $\alpha$ particles. A dominant static hyperfine interaction was observed from which a magnetic field at the nucleus of $2.6\le H\left(0\right)\mathrm{}\le 2.9$ MOe was deduced. This value is in agreement with the field calculated in the $\mathrm{LS}$ scheme. The static interaction may originate in a number of one- and two-electron processes that occur at the target surface.