Optogalvanic spectroscopy of the hyperfine structure of the $5p^65d$ ${}^2D_{3/2,5/2}$ and $5p^64f$ ${}^2F^o_{5/2,7/2}$ levels of La III

We measure the hyperfine structure of the $5p^65d$ ${}^2D_{3/2}$, $5p^65d$ ${}^2D_{5/2}$, $5p^64f$ ${}^2F^o_{5/2}$, and $5p^64f$ ${}^2F^o_{7/2}$ levels in doubly-ionized lanthanum (La III; La$^{2+}$) in a hollow cathode lamp using optogalvanic spectroscopy. Analysis of the observed spectra allows us to determine the hyperfine $A$ coefficients for these levels to be $A_{D3/2}=412(4)$ MHz, $A_{D5/2}=20(5)$ MHz, $A_{F5/2}=319(2)$ MHz, and $A_{F7/2}=155(4)$ MHz; and provide estimates for the hyperfine $B$ coefficients as $B_{D3/2}=105(29)$ MHz, $B_{D5/2}=157(40)$ MHz, $B_{F5/2}=-2(53)$ MHz, and $B_{F7/2}=171(51)$ MHz.