Electronic Band Systems of SF2 Radicals Observed by Resonance-Enhanced Multiphoton Ionization

Abstract

A pulsed dc electric discharge in a pulsed supersonic beam has been used as an efficient source of producing radicals. The (2+1) REMPI spectra of the SF2 radicals were investigated between 245 and 365 nm (54945−81630 cm-1 ). Eight electronic band systems have been observed in this range. One series with quantum defect δ = 1.961(6) is comprised of the B̃ 1B1(4s) and J̃ 1B1(5s) Rydberg states which have origins at ν0-0 = 54470 and 68951 cm-1, respectively. Vibrational analyses of these Rydberg states showed that in the B̃ 1B1(4s) state ω1‘(a1 sym str) = 981(23) cm-1 and in the J̃ 1B1(5s) state ω1‘(a1 sym str) = 942(3) cm-1. A second Rydberg series Ẽ (4p) with quantum defect δ = 1.61 is characterized with the spectroscopic values ν0-0 = 62025 cm-1, ω1‘(a1 sym str) = 941(27) cm-1, and ω2‘(a1, bend) = 413(12) cm-1. Incompletely rotational analysis revealed that the F̃ electronic state with ν0-0 = 63812 cm-1, ω1‘(a1 sym str) = 966(6) cm-1, and ω2‘(a1, bend) = 417(23) cm-1 merges with the vibrational progression of the Ẽ (4p) state. The F̃ state might be a 4p Rydberg state of another hybrid symmetry with the quantum defect δ = 1.50. A third Rydberg series is comprised of the G̃ (3d) (ν0-0 = 68378 cm-1, ω1‘ = 939(12) cm-1, δ = 0.086), the H̃ (3d) (ν0-0 = 68571 cm-1, ω1‘ = 936(4) cm-1, δ = 0.064), and the Ĩ (3d) (ν0-0 = 68847 cm-1, ω1‘ = 933(4) cm-1, δ = 0.032). In addition, two valence states labeled as the B̃‘ state (38623 cm-1) and C̃ state (56219−61278 cm-1) were also observed. A fit of the Rydberg formula to the ns(1B1) (n = 4,5) origins found the adiabatic ionization potential of SF2 radicals to be IPa = 10.021(1) eV.