Competition Between Two Excitation-dissociation Channels for Molecular Ions

When the molecular ions XYZ⁺(XY²⁺) are excited simultaneously from an electronic state E₀ into two higher electronic states E_α and E_β with supervened dissociation or predissociation, competition between the α and β excitation-dissociation channels occurs. A theoretical model is provided to deal with the competition of the two excitation-dissociation channels with more than two kinds of ionic products for XYZ⁺ (XY²⁺). Supposing that the photo-excitation rates of two states E_α and E_βare much less than their dissociation or pre-dissociation rates, a theoretical equation can be deduced to fit the measured data, which reflects the dependence of the product branching ratios on the intensity ratios of two excitation lasers. From the fitted parameters the excitation cross section ratios are obtained. In experiment, we studied the competition between two excitation-dissociation channels of CO²⁺. By measuring the dependence of the product branching ratio on the intensity ratio of two dissociation lasers and fitting the experiment data with the theoretical equation, excitation cross section ratios were deduced.