CALCULATION OF FERMI CONTACT HYPERFINE SPLITTING FOR SMALL ATOMS AND MOLECULES

Hyperfine splittings by the Fermi contact term are calculated for the atoms Li, B, C, N, O, F, Na, and the radicals OH, NH2, and CH3. The results of all atom calculations agree well with experiment. The errors are about 10% for the atoms and the radical OH; for the polyatomic radicals they are about +30% consistently. The results are obtained using (1) an extended Hartree-Fock method approximated in this paper by the use of the natural orbitals of UHF calculations; (2) properly prepared Gaussian functions instead of Slater-type functions. Errors in frequently used methods are discussed and specified by calculations. Simple formulas are given which relate the p-type splittings to the atomic number.