Abstract
The calculation of the coupling constants of the magnetic and electric hfs of the NO molecule is done using the Heitler-London wave function with Hartree atomic wave function. The homopolar ground state is found to be expressed by a linear combination of four Slater determinants. This wave function is used with success to calculate the spin-orbit coupling constant and the Λ-type doublet separation as well as the hfs coupling constants. The "s-character" of the magnetic hfs is explained by the configuration interaction with an excited state of the N atom, in which one of the 2s-electrons is promoted to the 3s orbital. The effective number of the odd electron in the electric hfs is 0.46, and Q for the N nucleus is 0.03×1024 cm2. No ionic structure needs to be considered.