A quantumhyphen;chemical investigation of the nitrogenndash;fluorine and phosphorusndash;fluorine diatomic systems is described. Molecular selfhyphen;consistenthyphen;field wavefunctions near the Hartreendash;Fock limit were computed via the Roothaan expansion method for theX3Sgr;minus;(ground),a1Dgr;, andb1Sgr;plus;states of NF and for the2Pgr;states of NFplus;and NFminus;. Similar wavefunctions were computed for the3Sgr;minus;ground state of PF and forPFplus;lpar;2Pgr;rpar;andPFminus;lpar;2Pgr;rpar;. For the neutral molecules, the experimental bond lengths were used; for the charged species, the internuclear separations of the parentlpar;3Sgr;rpar;molecules were used. In addition, a wavefunction was also obtained forPFplus;lpar;2Pgr;rpar;at its experimental internuclear separation. Values derived for the binding and ionization energies through the use of semiempirical correlation energies are in excellent agreement with experimental data; the uncorrelated excitation energies, as expected, are somewhat different than the experimental results. The electron affinities deduced from the wavefunctions indicate that the hitherto unreported NFminus;and PFminus;should be thermodynamically stable at moderate temperatures. Dipole and quadrupole moments have also been calculated for all the species. The second ionization potential of PF has been estimated based on Koopmans' theorem.
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