Study on the photofragment excitation spectrum of SO + 2 in the range of 281-332nm

With the preparing of SO + 2 ( 2 Ａ 1 ( 000)) by ［3+1］ multiphoton ioniz ation of the neutral SO 2 molecules at 380.85nm,the photofragment exci tation (P HOFEX) spectrum in ultraviolet (UV) (281-332nm) wavelength range has been obtain ed.The PHOFEX spectrum in the UV range was assigned essentially to the SO + 2 (,)←SO + 2 ( 2 Ａ 1 ) transitions.The transitions fr om 2 Ａ 1 (000) to the bend vibration levels of SO + 2 () were suggested,new harmon ic bend vibrational frequency ν 2 =241.78±0.92cm -1 and the anharmonicity constant X 22 =-1.71±0.01cm -1 for SO + 2 () was deduced.By using th e SO + PHOFEX spectra in UV and in visible range (562-664nm), the symm etry of ,, states of SO + 2 and the predissociation mechanism of SO + 2 (,,) were determined,that is,(i)the symmetry of ,, states of SO + 2 s hould be 2 B 2 ， 2 Ｂ 1 ， 2 Ａ 1 ，( ii) around ,, states there should be two r epulsive states of symmetry α 2 Ａ 2 and β 2 Ｂ 2 ，converging to the dissociation limit of SO + (X 2 П)+O( 3 P g ),(iii)the couplings betw een 2 B 1 and α 2 A 2 and betwee n 2 B 2 and β 2 Β 2 ,lead to the dissociation to S O + (X 2 П)+O( 3 Ｐ g ).