A spin-rotation-type modification of a $\gamma$-ray angular-distribution pattern has been observed in $\gamma$ rays emitted from ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ nuclei recoiling from a target tilted to the direction of recoil (which is also the beam direction and the symmetry axis). The spin rotation is ascribed to the effect of hyperfine interactions with ionic states that are polarized when the ions emerge from the tilted foil.

• Received 6 December 1976

DOI:https://doi.org/10.1103/PhysRevLett.38.221