Hyperfine Structures ofRe186andRe188

The atomic-beam magnetic-resonance "flop-in" technique has been used to determine the hyperfine-structure separations of the isotopes ${\mathrm{Re}}^{186}$ and ${\mathrm{Re}}^{188}$. The magnetic-dipole interaction constant $a$ and the electric-quadrupole interaction constant $b$ have been measured for these two radioactive isotopes in the $J=\frac{5}{2}$ ground state. Beams were produced by electron bombardment of irradiated rhenium wires. The spins of both isotopes had been determined previously to be 1. For the interaction constants of ${\mathrm{Re}}^{186}$ we obtained $a_{186}=\pm 78.3058\left(24\right)\mathrm{}$ Mc/sec, $b_{186}=\mp 8.3601\left(50\right)\mathrm{}$ Mc/sec. These give values for the two hyperfine-structure separations of $\Delta {\nu }_{186}(\frac{7}{2},\frac{5}{2})=\pm 265.292\left(14\right)\mathrm{}$ Mc/sec, $\Delta {\nu }_{186}(\frac{5}{2},\frac{3}{2})=\pm 208.305\left(14\right)\mathrm{}$ Mc/sec. For the interaction constants of ${\mathrm{Re}}^{188}$ we obtained $a_{188}=\pm 80.4320\left(32\right)\mathrm{}$ Mc/sec, $b_{188}=\pm 7.7455\left(60\right)\mathrm{}$ Mc/sec. These give values for the two hyperfine-structure separations of $\Delta {\nu }_{188}(\frac{7}{2},\frac{5}{2})=\pm 273.379\left(13\right)\mathrm{}$ Mc/sec, $\Delta {\nu }_{188}(\frac{5}{2},\frac{3}{2})=\pm 212.698\left(17\right)\mathrm{}$ Mc/sec. The nuclear moments of both isotopes were determined to be positive. Also obtained was an improved value for the electronic Landé $g$ factor for rhenium: $g_J=-1.95203\mathrm{}\left(8\right)\mathrm{}$.