Calculation of the hyperfine structure of the superheavy elements Z=119 and Z=120+

The hyperfine structure constants of the lowest $s$ and $p_{1\mathrm{/}2}$ states of superheavy elements Z=119 and Z= 120${}^{+}$ are calculated using {\em ab initio} approach. Core polarization and dominating correlation effects are included to all orders. Breit and quantum electrodynamic effects are also considered. Similar calculations for Cs, Fr, Ba${}^{+}$ and Ra${}^{+}$ are used to control the accuracy. The dependence of the hyperfine structure constants on nuclear radius is discussed.