F we calculate to the same degree of approximation &~t he electronic energy levels of a molecule and of its ion, we are able (1) to obtain an extensive insight into the adiabatic potential curves, (2) to avoid arguments concerning physically meaningless results, and(3) to evaluate the ionization potential, the energies of the states in the Rydberg region, and other quantities having experimental importance.Fluorine has the following characteristics as compared with the other second-row elements. The ratio of the atomic radius' to interatomic distance in diatomic fluorine is very small. In Table I this ratio is given for several diatomic molecules. We expect, therefore, that Quorine keeps its "atomic" character in the molecule.
The energy levels of the fluorine molecules F2 are calculated by ASMO method. First and second quantum orbitals and configurations therefrom are all taken into account, resulting in Do= 1.99 ev and R,= 1.41 A. Vertical excitation energies of 12;g+_1I1u and 12;g+_3I1g are 5.21 ev and 3.93 ev, respectively. The importance of the configurations and of the inner-shell electrons to the ground state is discussed. Finally the ionicities of the states are evaluated.'
The same ASMO treatment as in Part I [K. Hijikata, J. Chem. Phys. 34, 221 (1961), preceding paper] is applied to the fluorine molecule with several pairs of effective nuclear charges, and the best value of the effective nuclear charge is determined for each state. The ground state 1Σg+ has De=2.02 ev, Re=1.437 A and the effective nuclear charge 2.58. It is found that the explanation for the effective nuclear charge of each state from the ``atomic point of view'' is difficult. The vertical excitation energies 1Σg+—1Πu, 1Σg+—3Πu, and 1Σg+—1Πg are calculated to be 4.49, 3.73, and 6.50 ev, respectively. The lower energy levels of the molecular ion F2+ are also calculated, showing that the ground state is 2Πg, that two more states appear to have potential minima, and that the higher energy levels of F2 calculated by ASMO are almost meaningless except 1Σu+. The energy level of this ionic state 1Σu+ at R=1.625 A is 10.8 ev above the minimum of 1Σg+. The energy diagram summarizing the calculations is shown. The discrepancy is indicated between the experimental and the theoretical ionization potentials.
Articles you may be interested inA multireference configuration interaction study of the hyperfine structure of the molecules CCO, CNN, and NCN in their triplet ground states Orientation, alignment, and hyperfine effects on dissociation of diatomic molecules to open shell atoms By means of a 23-dimensional configuration interaction calculation the energy and eigenfunction of the ground 'II state are determined resulting in dissociation energy of 2.2 ev. The magnetic hyperfine and nuclear quadrupole coupling constants are calculated from this molecular function. The contact term 1 q, (0) I' is obtained as 0.71 X 10-24 cm-3 which agrees well with experiment. The values of «3 cos'x-1)u/r3)Av, (sin'x/r3)Av, and (r-3 )Av are not much affected by the configuration interactions.
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