The Hyperfine Structure and Nuclear Moments ofPr141

The hyperfine structure of the ground state of ${\mathrm{Pr}}^{141}$ has been studied by the atomic beam magnetic resonance method. It has been established that the electronic ground state of Pr is $4f^{3}6s^2$, ${}_{}{}^4{}_{}{}^{}I_{\frac{9}{2}}^{}{}_{}{}^{}$. Of the five hyperfine intervals arising from this electronic state and a nuclear spin of $\frac{5}{2}$, the lowest two have been observed. They are $W(F=4\mathrm{})-W(F=3\mathrm{})=3708.05\mathrm{}$ Mc/sec and $W(F=3\mathrm{})-W(F=2\mathrm{})=2782.25\mathrm{}$ Mc/sec. If the hfs is assumed to be entirely due to an interaction between the ${}_{}{}^4{}_{}{}^{}I_{\frac{9}{2}}^{}{}_{}{}^{}$ state and the nucleus, the observed intervals may be expressed in terms of a magnetic dipole interaction constant $A$ and a nuclear electric quadrupole interaction constant $B$. It is found that $A=926.03\mathrm{}\pm 0.1$ Mc/sec and $B=-13.9\mathrm{}\pm 1.0$ Mc/sec. From these constants, the nuclear moments have been evaluated by means of approximate methods. The values obtained are $\mu =+3.8\mathrm{} \mathrm{nm}, Q=-0.054\mathrm{}\times {10}^{-24\mathrm{}} {\mathrm{cm}}^2.$