HYPERFINE FIELD OF FRANCIUM IN IRON

The hyperfine field of francium in iron has been measured for different isotopes using the method of low-temperature nuclear orientation and samples prepared by ion implantation at $Tl~1\mathrm{K}.$ For ${}^{208}\mathrm{Fr}$ a nuclear magnetic resonance was observed. From the center frequency ${\ensuremath{\nu}}_{L}{(B}_{\mathrm{ext}}=0\mathrm{}\mathrm{T})=490.7(4)\mathrm{MHz},$ we derive the corresponding magnetic hyperfine field as ${B}_{\mathrm{hf}}(\mathrm{Fr}Fe)=94.9(4)\mathrm{T}.$