Study on the photodissociation and symmetry of SO 2 + (D) Zhong Wang, Limin Zhang, Shuqin Yu, Shilin Liu, Xingxiao Ma 中国科学技术大学 University of Science & Technology of China

The structures of SO 2 and SO 2 + C 2v

Spectroscopy L.Wang, Y.T.Lee, and D.A.Shirley, J.Chem.Phys. 87, 2489 (1987) H.D.Eland and C.J.Danby, Int.J.Mass Spectrom.Ion Phys. 1, 111 (1968) D.R.Lloy and P.J.Roberts, Mol.Phys. 26, 225 (1973) G.Dujardin and S.Leach, J.Chem.Phys. 75, 2521 (1981) Photodissociation G.Dujardin and S.Leach, Dynamics J.Chem.Phys. 75, 2521 (1981) K.Norwood and C.Y.Ng, J.Chem.Phys. 93, 6440 (1990) T.F.Thomas, F.Dale, and J.F.Paulson, J.Chem.Phys. 84, 1215 (1986) S.P.Goss, R.G.McLoughlin and J.D.Morrison Int. J. Mass Spectrom. Ion. Proc.64, 213 (1985) Previous Studies

Two interesting questions ！ 1 ． The symmetries of C, D and E excited states ？ The C, D and E excited states of SO 2 + overlap each other and are located at the third complex photoelectron band of SO 2 which is disperse at the high electron energy. 2 ． The dissociation mechanism of SO 2 + ？

 The PHOFEX spectrum in the wavelength The PHOFEX spectrum in the wavelength range of 281 ～ 332 nm (UV)  The PHOFEX spectrum in the wavelength The PHOFEX spectrum in the wavelength range of 563 ～ 660 nm (Visible) Experimental Results

The PHOFEX spectrum of SO 2 + obtained by monitoring SO + ions in the wavelength range of 281~332 nm.

Band position and assignments for the fragment SO + excitation spectrum of SO 2 + The constants of spectroscopy  SO 2 + (D) new harmonic bend vibrational frequency 2 =  0.92 cm -1 the anharmonicity constants X 22 =  1.71  0.01 cm -1

Dependence of SO + ion signal on laser intensity in double logarithmic form One-photon excitation

The PHOFEX spectrum of SO 2 + was obtained by monitoring SO + ions in the wavelength range of 563 ～ 660 nm

Dependence of SO + ion signal on laser intensity in double logarithmic form [1+1] two-photon excitation

Compare the PHOFEX spectrum in (281 ～ 332 nm) with it in （ 563 ～ 660 nm ） same Reach the same energy position (281 ～ 332 nm) Obvious resonance band structure ; Be assigned ( 563 ～ 660 nm ) Without discernible band structure; continuous Different

 2 A 2 repulsive state One photon excitation : Two photons excitation : SO 2 + : C 2v point group symmetry

The possible vibrational mode: a 1 and b 2 B 1  b 2 = A 2 The symmetry of the D state is 2 B 1

Conclusion:  We give proof on experiment that around SO 2 + (D) there exists a repulsive state 2 A 2 converging to the dissociation limit of SO + (X 2 П)+O( 3 P g ).  It is confirmed that the symmetry of the D state is 2 B 1.

Acknowledgement Laboratory of Bond Selective Chemistry, Department of Chemical Physics, University of Science and Technology of China. Gas-phase Molecular Dynamics group, Department of Chemistry, Brookhaven National Laboratory, U.S. Thanks for your attention

The [3+1] REMPI spectrum of SO nm

The TOF mass spectra averaged over 256 laser shots and obtained with (a) only the photoionization laser at nm, (b) only the photodissociation laser at nm, and (c) both the photoionization laser and the dissociation laser. (a) (b) (c)