Abstract
The atomic shielding factor is conveniently defined from the molecular shielding factor which is derived by the application of perturbation theory to a homonuclear diatomic molecule, and is applied to predict the force constants of heteronuclear diatomic molecules. Especially, it is stressed that the atomic shielding factors for alkali atoms can be selected to be nearly zero and shown that for molecules (ij) containing alkali atoms (i) there exists a simple relationship Kij = (Nj+1)e2/?3ij, where Kij and ?ij are the force constant and the equilibrium internuclear distance, respectively, e is the electronic charge, and Nj is the number of electrons of atom (j) which are outside a complete shell.