Recoil into vacuum g-factor measurement of the 5/2+ state at 0.350 MeV in 21Ne

Reports the investigation of the hyperfine interaction in 21Ne atoms at a recoil velocity β = 3.05%. At this recoil velocity, three- and four-electron ions dominate. The hyperfine interaction in the ground-state configuration is very weak for the three-electron ion and absent for the four-electron ion. An important hyperfine interaction, if observed can come only from excited electron configurations. Metastable states generally have lifetimes long compared to the nuclear lifetimes and may contribute to the hyperfine interaction. The main contributions come from configurations with unpaired 1s electrons, which produce high magnetic fields at the nucleus. The method employed for the observation of the hyperfine perturbation is simular to the recoil distance technique widely used for the measurement of nuclear lifetimes. (Auth.)