SLOWING-DOWN OF 3-EV SM IONS IN EU COMPOUNDS

Slowing down of ions at ultralow velocities has been studied in the ca se of 0.02-eV/amu Sm-152 recoils in EuF2, EuF3, EuCl3, and EU(2)O(3). The recoiling atoms were produced in beta decay of Eu-152. The Doppler -broadened 842- and 963-keV gamma-rays emitted by the recoiling Sm-152 nuclei were detected by a crystal spectrometer. The experimental gamm a-ray line shapes were simulated by molecular-dynamics technique using empirically derived interatomic pair potentials. The lifetime of 28 /- 6 fs was deduced for the first excited state at 963 keV in Sm-152.