Hyperfine structure investigation of 70As with the ABMR method

The hyperfine structure of 53 min 70As has been studied with the atomic beam magnetic-resonance (ABMR) method in a new two-pole type atomic beam apparatus. Resonance experiments at a very low homogeneous magnetic field (0.2 G) yield a value I = 4 for the nuclear spin of 70As, in agreement with an assignment from beta decay studies. Resonance experiments at magnetic fields up to 5 G yield a preliminary value mod(a) = 36(3) MHz for the magnetic dipole coupling constant. A comparison with the hyperfine constant and nuclear moment of the stable isotope 75As yields a nuclear magnetic moment mod(μ) = 2.1(2) n.m. for 70As. A calculation of the magnetic moment on the basis of the single-particle model results in a value μ = 1.78 n.m. (Auth.)