Energy disposal in photodissociation from magic angle measurements with a crossed high-energy ion beam and laser beam: Photodissociation dynamics of the (N2)+2 cluster in the 458–514 nm range

The principle behind obtaining photoproduct kinetic energy distributions from magic angle measurements with a crossed high-energy ion beam and laser beam is discussed and the results of an investigation of the photodissociation of the (N2)+2 cluster in the 458–514 nm range are reported. The N+2 product kinetic energy distributions are smooth and peak at relatively large values of kinetic energy (∼0.5 eV). An average product rotational excitation of at least 0.15 eV must occur since the product vibrational states were not resolved. A plot of the average product relative kinetic energy against the available energy is linear and can be accounted for using a simple impulsive model plus vibrational excitation due to geometry changes. The product angular distributions have the form 1+βP2(cos θ) with β=1.15–1.35 (with a linearly polarized laser). The effects of reactant ion rotation on the value of β were explored using a crude model and found to be small. The results indicate that photodissociation of (N2)+2 occurs by a direct transition to a repulsive surface. The transition is predominantly (>90%) 2Σ←2Σ and there was no evidence for the formation of electronically excited products.