Comparison of configuration‐interaction methods for F 2

Configuration‐interaction calculations for F 2 have been carried out at several inter‐nuclear distances using a minimum Slater‐type atomic orbital basis set. Configurations were constructed in three ways: with approximate Hartree‐Fock molecular orbitals, with symmetry orbitals, and with atomic orbitals themselves. By comparing various calculations in the three schemes, we conclude that K ‐shell and π orbital excitations are not important within the chosen basis set, that minimal “valence‐configuration” calculations are far better than minimal Hartree‐Fock results, and that the main error in “valence‐configuration” studies of F 2 can probably be removed by a more extended expansion which includes the use of open‐shell configurations.