Relativistic and QED corrections to one-bond indirect nuclear spin-spin couplings in X^2+_2 and X^2+_3 ions (X = Zn, Cd, Hg)

COLOMBO JOFRÉ, MARIANO TOMÁS; KOZIOL, KAROL; AUCAR, IGNACIO AGUSTÍN; GAUL, KONSTANTIN; BERGER, ROBERT; AUCAR, GUSTAVO ADOLFO

JOURNAL OF CHEMICAL PHYSICS

AMER INST PHYSICS

Lugar: New York; Año: 2022 vol. 157 p. 64103 - 64103

0021-9606

The indirect spin-spin coupling tensor, $m J$, between mercury nuclei in systems containing this element can be of the order of few kHz and one of the largest measured. We analysed the physics behind the electronic mechanisms that contribute to the one- and two-bond couplings $^n m{J}_{mathrm{Hg}-mathrm{Hg}}$ ($n=1, 2$). For doing so, we performed calculations for $J$-couplings in the ionized $X_2^{2+}$ and $X_3^{2+}$ linear molecules ($X$ = Zn, Cd, Hg) within polarization propagator theory, using the random phase approximation and the pure zeroth--order approximation with Dirac--Hartree--Fock and Dirac--Kohn--Sham orbitals, both at four-component and ZORA levels. We show that the ``paramagnetic-like´´ mechanism contribute with more than 99.98% to the total isotropic value of the coupling tensor. By analyzing the molecular and atomic orbitals involved in the total value of the response function, we find that the $s$-type valence atomic orbitals have a predominant role in the description of the coupling. This fact allows us to develop an effective model from which QED effects on $J$-couplings in the aforementioned ions can be estimated. Those effects were found to be within the interval $(0.7;~1.7)$% of the total relativistic effect on isotropic one-bond $^1m{J}$ coupling, though ranging those corrections between the interval $(-0.4;~-0.2)$% in Zn-containing ions, to $(-1.2;~-0.8)$% in Hg-containing ions, of the total isotropic coupling constant in the studied systems. The estimated QED corrections show a visible dependence on the nuclear charge $Z$ of each atom $X$ in the form of a power-law proportional to $Z_X^5$.