Hyperfine Structure and Nuclear Moments of 20.4-Min C11

We have measured the hyperfine structure in the $^{3}P_{2}$ and $^{3}P_{1}$ states of the ground state configuration of ${\mathrm{C}}^{11}$ by the atomic-beam magnetic-resonance technique. The values obtained after corrections for perturbations by nearby fine-structure states are $^{3}P_{2}$: $\frac{A}{h}=(\ensuremath{-})68.203\ifmmode\pm\else\textpm\fi{}0.007$ Mc/sec, $\frac{B}{h}=(\ensuremath{-})4.949\ifmmode\pm\else\textpm\fi{}0.028$ Mc/sec; $^{3}P_{1}$: $\frac{A}{h}=(\ensuremath{-})1.242\ifmmode\pm\else\textpm\fi{}0.010 \mathrm{Mc}/sec or (\ensuremath{-})1.200\ifmmode\pm\else\textpm\fi{}0.010 \mathrm{Mc}/sec$ depending upon the choice of zero-field level ordering, where $B(J=1)=\ensuremath{-}\frac{B(J=2)}{2}$. From these data it is possible to calculate the nuclear moments of the mirror nucleus, ${\mathrm{C}}^{11}$, using a theoretical value of $〈\frac{1}{{r}^{3}}〉$ for the $p$ electrons. The results are ${\ensuremath{\mu}}_{I}=(\ensuremath{-})1.027\ifmmode\pm\else\textpm\fi{}0.010$ nm, ${Q}_{\mathrm{uncorrected}}=(+)(0.0308\ifmmode\pm\else\textpm\fi{}0.0006)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}24}$ ${\mathrm{cm}}^{2}$. No signs were measured in these experiments; the indicated signs assume ${\ensuremath{\mu}}_{I}<0$ in ${\mathrm{C}}^{11}$. A value of 1.5011\ifmmode\pm\else\textpm\fi{}0.0006 for ${g}_{J}$ was also obtained in the $^{3}P_{2}$ state.