Polarization of Silver Nuclei in Metallic Iron and Nickel

Abstract

Nuclei of ${\mathrm{Ag}}^{104}$ and ${\mathrm{Ag}}^{110m}$ were polarized at temperatures between 0.0105 and 0.97°K, employing the large hyperfine magnetic fields induced at the nuclei of silver atoms dissolved in iron and in nickel. The temperature and angular dependences of $\gamma$-ray angular distributions were used to determine the magnitudes of the hyperfine structure constants. Nonconservation of parity in beta decay was used to determine the signs of the internal fields, using germanium detectors to count positrons from ${\mathrm{Ag}}^{104}$ and electrons from ${\mathrm{Ag}}^{110m}$. The hyperfine fields were found to be negative in both iron and nickel. Analysis of the $\gamma$-ray data on one-hour ${\mathrm{Ag}}^{104}$ yielded approximate values for the internal fields: $H_i\left(\mathrm{Ag}\mathrm{in}\mathrm{Fe}\right)=-350\mathrm{}\pm 100$ kG, $H_i\left(\mathrm{Ag}\mathrm{in}\mathrm{Ni}\right)=-108\mathrm{}\pm 30$ kG. Cobalt-60 $\gamma$-ray thermometry was used, and the problems of thermometry at 0.01°K are discussed. Nuclear spins of four levels in ${\mathrm{Cd}}^{110}$ were determined unambigously, confirming earlier work, which was re-interpreted where necessary. The energy levels (spins) are 2162 keV (3+), 2219 keV(4+), 2479 keV(6+), 2926 keV(5+). The 1384-keV $\gamma$ ray in ${\mathrm{Cd}}^{110}$ was found to be (91.7±2.8)% magnetic dipole and (8.3±2.8)% electric quadrupole. The 1505-keV $\gamma$ ray was (78.9±4.8)% magnetic dipole and (21.1±4.8)% electric quadrupole. An approximate value of +2.9±1.3 nm was determined for the nuclear moment of ${\mathrm{Ag}}^{110m}$.