Is E112 a relatively inert element? Benchmark relativistic correlation study of spectroscopic constants in E112H and its cation

We report the first results of relativistic correlation calculation of the spectroscopic properties for the ground state of E112H and its cation in which spin-orbit interaction is taken into account non-perturbatively. Studying the properties of E112 (eka-Hg) is required for chemical identification of its long-lived isotope, $^{283}$112. It is shown that appropriate accounting for spin-orbit effects leads to dramatic impact on the properties of E112H whereas they are not so important for E112H$^+$. The calculated equilibrium distance, $R_e^{calc}=1.662$ A, in E112H is notably smaller than $R_e^{expt}=(1.738\pm0.003)$ A and $R_e^{calc}=1.738$ A in HgH, whereas the dissociation energy, $D_e^{calc}=0.42$ eV, in E112H is close to $D_e^{expt}=0.46$ eV and $D_e^{calc}=0.41$ eV in HgH. These data are quite different from $R_e^{NH}=1.829$ A and $D_e^{NH}=0.06$ eV obtained for E112H within the scalar-relativistic Douglas-Kroll approximation [Nakajima and Hirao, Chem. Phys. Lett., 329, 511 (2000)]. Our results indicate that E112 should not be expected to be "more inert" than Hg in opposite to the results by other authors.