Calculation of thallium hyperfine anomaly

We suggest a method to calculate hyperfine anomaly for many-electron atoms and ions. At first, we tested this method by calculating hyperfine anomaly for hydrogen-like thallium ion and obtained fairly good agreement with analytical expressions. Then we did calculations for the neutral thallium and tested an assumption, that the the ratio between the anomalies for $s$ and $p_{1/2}$ states is the same for these two systems. Finally, we come up with recommendations about preferable atomic states for the precision measurements of the nuclear $g$ factors.