ENERGETICS, STRUCTURE AND PHOTODISSOCIATION DYNAMICS OF THE CLUSTER AR.N-2+

A mass selected ion beam of ArN2+ clusters is brought to a spatial focus and crossed with the polarized output of an argon ion laser. Photofragment ions are mass and energy analyzed using an electrostatic analyzer and detected using single ion counting methods. Photoproducts observed over the photon energy range of 2.1 to 3.5 eV are Ar + /N2 and N2+ /Ar with the former favored by about a factor of 3. Analysis of the data indicate the upper state is purely repulsive leading to strongly translationally and vibrationally excited products. The absolute cross section has an onset at about 600 nm and smoothly increases to 357 nm. In order to reasonably interpret the data it is suggested the higher energy Ar + (2P3/2 )/N2 asymptote diabatically correlates to the ground state of ArN2+ and the lower energy N2+ (X2Σ)/Ar asymptote diabatically correlates to the repulsive state accessed by the photon. Detailed dynamics in the region where the curves cross are responsible for the observed product distribution. Application of an impulsive model indicates the ground state of ArN2+ is linear. Finally, equilibrium measurements of the reaction (N2)2+ + Ar↔ArN2+ + N2 indicate ΔH 00 = - 1.0 ± 0.3 kcal/mol and ΔS0 = 1.5 ± 0.5 cal k-1 mol-1 in agreement with the result of Teng and Conway which had been disputed in the literature. © 1990 American Institute of Physics.