Spectra of jet - cooled 32 SO 2 and 34 SO 2 in systems ã 3 B 1 and b̃ 3 A 2 – X̃ 1 A 1 : Rotational structure of perturbed b̃ 3 A 2

Spectra of ã B1(n1n2n3)5(110) and (200) – X̃ A1(000) of SO2 and SO2 are obtained in a supersonic jet at a resolution 0.015 cm. The rotational structures are analyzed for both isotopic species to obtain precise rotational and spin constants. Two new bands at 27 032.222~1! and 27 515.41~1! cm arising from vibronic interaction separately with vibrational state ~110! and ~200! of ã B1 are assigned to transitions to b̃ A2(011) and ~101!. The rotational structure of b̃ A2 is observed and analyzed for the first time. The two vibrational states are analyzed to yield effective rotational constants A51.4348(3), 1.89~3!, B50.3610(3), 0.412~3!, and C50.2689(3), 0.239~3! cm, respectively. Then the difference n12n2 of vibrational frequency of b̃ A2 is obtained to be 483.19 cm. Because of interaction to b̃ A2(011) the observed spacing of K stack and spin constants a and b for ã B1(110) are smaller whereas the state ã B1(200) is relatively unaffected and only spin constants vary significantly. © 2001 American Institute of Physics. @DOI: 10.1063/1.1333019#