Ab initio calculations of off-diagonal hyperfine interaction in cesium

We have performed a relativistic many-body calculation of the off-diagonal hyperfine interaction mixing amplitude $M_{\mathrm{hf}}$ for the $6s-7s$ transition in atomic cesium. The ab initio result $M_{\mathrm{hf}}=0.8070\mathrm{}\left(73\right)\mathrm{}\times {10}^{-5}|{\mu }_{\mathrm{B}}/c|$ is in excellent agreement with a previous semiempirical value $M_{\mathrm{hf}}=0.8094\mathrm{}\left(20\right)\mathrm{}\times {10}^{-5}|{\mu }_{\mathrm{B}}/c|.$