Studies on the photodissociation and symmetry of $SO2+(D̃)$

With the preparing of $SO2+(X̃ 2A1(000))$ by $[3+1]$ multiphoton ionization of the neutral $SO2$ molecules at 380.85 nm, the photodissociation process and the symmetry of the excited states $D̃$ of $SO2+$ molecular ions has been investigated by measuring the photofragment $SO+$ excitation (PHOFEX) spectrum in ultraviolet (282–332 nm) and in visible (562–664 nm) wavelength ranges, respectively. The $D̃(v100),$ $D̃(0v20)←X̃ 2A1(000)$ transitions of $SO2+$ were assigned in the PHOFEX spectrum in the UV range. By comparing the discernible PHOFEX spectrum in UV range with the continuous PHOFEX spectrum in visible range, it is deduced that (i) around $SO2+(D̃)$ there exists a repulsive state $α 2A2$ converging to the dissociation limit of $SO+(X 2Π)+O(3Pg),$ (ii) the coupling between $SO2+(D̃)$ and $SO2+(α 2A2)$ leads to the dissociation to $SO+(X 2Π)+O(3Pg),$ (iii) the symmetry of $D̃$ state is $D̃ 2B1.$