The nuclear lighthouse effect

has been applied to samarium-149. The NLE technique was developed last year by researchers from the University of Rostock in Germany. It allows physicists to get very accurate lifetime measurements of certain short-lived nuclear resonances. In their recent work, the Rostock scientists mounted a thin sheet of ¹⁴⁹Sm₂O₃ on the inside wall of a small cylinder. They then placed the cylinder in an x-ray beam at the Advanced Photon Source at Argonne National Laboratory and spun it at 15 kHz with jets of pressurized air. The nonresonant x rays went straight through the rotor, while those that were absorbed by the nuclei were reemitted after some slight delay. That delay provided enough time for the cylinder to rotate a few milliradians, and the forward-scattered resonant x rays were thus deflected into a detector. The group detected a resonance energy of 22.496 keV with a natural lifetime...