Electronic Band Systems of SF_2 Radicals Observed by Resonance-Enhanced Multiphoton Ionization

摘要

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 SF_2 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 B-tilde ~1B_1(4s) and J-tilde ~1B_1(5s) Rydberg states which have origins at v_(0-0) = 54470 and 68951 cm~(-1), respectively. vibrational analyses of these Rydberg states showed that in the B-tilde ~1B_1(4s) state ω_1'(a_1 sym str) = 981(23) cm~(-1) J-tilde ~1B_1(5s) state ω_1'(a_1 sym str) = 942(3) cm~(-1). A second Rydberg series E-tilde (4p) with quantum defect δ = 1.61 is characterized with the spectroscopic values v_(0-0) = 62025 cm~(-1), ω_1'(a_1 sym str) = 941(27) cm~(-1), and ω_2'(a_1, bend) = 413(12) cm~(-1). Incompletely rotational analysis revealed that the F electronic state with v_(0-0) = 63812 cm~(-1), ω_1'(a_1 sym str) = 966(6) cm~(-1), and ω_2'(a_1, bend) = 417(23) cm~(-1) merges with the vibrational progression of the E-tilde (4p) state. The F-tilde 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 G-tilde (3d) (v_(0-0) = 68378 cm~(-1), ω_1' = 939(12) cm~(-1), δ = 0.086), the H-tilde (3d) (v_(0-0) = 68571 cm~(-1), ω_1' = 936(4) cm~(-1), δ = 0.064), and the I-tilde (3d) (v_(0-0) = 68847 cm~(-1), ω_1' = 933(4) cm~(-1), δ = 0.032). In addition, two valence states labeled as the B-tilde' state (38623 cm~(-1)) and C-tilde state (56219-61278 cm~(-1)) were also observed. A fit of the Rydberg formula to the ns(~1B_1) (n = 4,5) origins found the adiabatic ionization potential of SF_2 radicals to be IP_a = 10.021(1) eV.