Relativistic calculations of the rotational g factor of the hydrogen halides and noble gas hydride cations

The rotational g factors of the hydrogen halides, HX (X = F, Cl,Br,I), and noble gas hydride cations, XH+ (X = Ne,Ar,Kr,Xe), have been calculated at t he level of the random phase approximation (RPA) as relativistic four-compo nent linear response functions as well as nonrelativistic linear response f unctions. In addition, using perturbation theory with the mass-velocity and Darwin operators as perturbations, the relativistic corrections have been estimated as quadratic response functions. It was found that the four-compo nent relativistic calculations give in general a more negative electronic c ontribution to the rotational g factor than the nonrelativistic calculation s with relativistic corrections ranging from 0.2% for HF and NeH+ to 2.9% f or XeH+ and 3.5% for HI. The estimates of the relativistic corrections obta ined by perturbation theory with the mass-velocity and Darwin operators are in good agreement with the four-component results for HF, HCl, NeH+, and A rH+, whereas for HI, KrH+, and XeH+ they have the wrong sign. (C) 2001 Amer ican Institute of Physics.