Atomic Hyperfine Structure. III. Excited States of C,N, and O

Using restricted Hartree-Fock (RHF) wave functions and two previously defined types of configuration-interaction (CI) wave functions - the polarization wave function and the firstorder wave function - we have made ab initio calculations of the hyperfine structure (hfs) of ¹D C, ²D N, ²P N, and ¹D O. The hyperfine parameters of these excited states exhibit some interesting effects not encountered in the hfs of the ground states of first-row atoms. In particular, both ²D N and ²P N show no electric-quadrupole hfs in the RHF approximation. However, both the polarization and first-order wave functions predict a small electric-quadrupole hfs for these states of N¹⁴. Radford and Evenson have experimentally studied the hfs of ²D N, and our CI results are in good agreement (usually within experimental error) with their hfs constants. As was found previously for the ground states of N,O, and F, the polarization wave function gives better agreement with the experimental hfs than does the first-order wave function. The present results also indicate that the hfs parameters |ψ(0)|², 〈r_l^-3〉, 〈r_s^-3〉, and 〈r_q^-3〉 are not usually transferable between different states of the same atom.