Theoretical predictions concerning low-lying excited electronic states of sulfur difluoride, SF 2

Abstract

Ab initio computations with split-valence plus polarization plus diffuse Rydberg function basis sets at SCF and CI levels have been used to predict the four lowest lying electronic excited states of sulfur difluoride. Calculations on the 1A 1 ground state of SF 2 are in good agreement with the experimental structure and vibrational frequencies. The 6–31 G*R (s, p) CISD prediction for r(SF) is 1.621 versus 1.589 Å experimentally and θ(FSF) is 99.02° versus 98.3° experimentally. SCF harmonic vibrational frequencies scaled by 0.9 for the ground state are ν 1 = 844, ν 2 = 342, ν 3 = 831 cm −1 and on average deviate 1.5% from the experimental values of 840, 357 and 809 cm −1, respectively. The lowest 1,3A 2 and 1,3B 1 electronic states of SF 2 have been examined theoretically. Vertical excitation energies at the CISD level were (in eV); 3A 2 2.99, 1A 2 3.92, 3B 1 4.25, and 1B 1 5.77. Substantial changes in excited state energies were observed upon geometry relaxation. Most notably the adiabatic excitation energy to the 1B 1 state is only 2.42 eV. Such an excitation energy is consistent with the tentatively assigned emission spectrum of SF 2. Results on the SF 2 excited state vibrational frequencies are also presented in comparison with recent experimental work.