Photofragment ion imaging from mass-selected Mg⁺BrCH₃ complex: Dissociation mechanism following photoinduced charge transfer

We have observed fragment ion images produced by ultraviolet photodissociation of Mg⁺BrCH₃ complex ions using a reflectron time-of-flight mass spectrometer combined with an imaging detector. The BrCH₃⁺ fragment ion was produced after the 266-nm excitation of Mg⁺BrCH₃. In the image of the BrCH₃⁺ ions, a split distribution was observed parallel to the polarization direction of the photolysis laser. In calculated potential energy curves, we found a repulsive potential correlated with a dissociation limit of Mg + BrCH₃⁺: The calculation results indicate that the dissociation and the charge transfer occurred via non-adiabatic process after the 5²A′ ← 1²A′ photoexcitation. The obtained energy and angular distributions of BrCH₃⁺ photofragments were consistent with the fast BrCH₃⁺ formation process on the repulsive potential energy curve.