Hyperfine Structure in the 2084-keV State ofCe140

Differential perturbed angular-correlation measurements were made on the 2084-keV state of ${\mathrm{Ce}}^{140}$ in aqueous solution at room temperature, and in lanthanum metal both at room temperature and at 77°K. The derived $g$ factor of +1.014±0.038 is compared with Rho's theory and with other experimental values. The advantages of working with metals and at low temperatures are discussed. An upper limit of approximately 200°K is set on the quantity $\Delta E$, where $\frac{\Delta E}{k}$ is the energy spacing between ${\Gamma }_7$ and ${\Gamma }_3$ for ${\mathrm{Ce}}^{3+}$ in La metal. An approximate value of 4.1±0.4 atomic units is derived for $〈r^{-8\mathrm{}}〉$ of the cerium $4f$ electron, using the above upper limit for $\Delta E$.