Ab initio MO calculations of hyperfine coupling constants. A basis set study for 19F, 35Cl, 19F,and 35Cl

Hyperfine coupling constants (HFCC ) of the ¹⁹F and ³⁵Cl atoms and the ¹⁹F and ³⁵Cl radical anions have been calculated by the unrestricted Hartree–Fock (UHF ) method using polarization and diffuse functions with contracted double-zeta as well as uncontracted basis sets. The A_dip values are fairly insensitive to changes in the basis set and show good accordance with experimental and other theoretical studies. The isotropic HFCCS a_N of ¹⁹F, ¹⁹F, and ³⁵Cl show strong dependence on d functions and the state of contraction of the s, p set. Spin-projected UHF wave functions lead to better agreement with experiment.