Hyperfine structure and nuclear moments of protactinium-233

Abstract

By means of the atomic-beam magnetic resonance method using radioactive detection, the hyperfine structure of 91Pa 233 ( T 1 2 = 27.4 days ) has been investigated. Three low-lying states are found to be present in the beam, characterized by electronic angular momenta J = 11 2 , 9 2 and 7 2 and g values gj = −0.8141(4), −0.8062(15) and −0.7923(15) respectively. From these results it is inferred that the ground-state configuration of protactinium is almost certainly (5f) 2(6d) 1(7s) 2. The nuclear spin is measured and found to be I = 3 2 and the magnetic dipole and electric quadrupole hyperfine structure coupling constants are measured to be A = ±595(30) MHz and B = ∓2400(300)MHz respectively. From a direct measurement, the nuclear moment is found to be μ I = +3.4(0.8) n.m. From the hyperfine-structure constants and detailed calculations involving the electronic wave functions, the quadrupole moment is inferred to be Q = −3.0 barns.