The A2Πi → X2Πr visible band system of SO+ has been recorded photographically at high resolution. Molecular constants for the A and X states have been fitted to the measured line positions of the 0–5, 0–6, 1–5, and 1–6 bands. Λ-type doubling was resolved completely for most of the lines of the 2Π1/2 – 2Π1/2 sub-bands, and has led to the first reported values of the splitting constants p′ and p″. All the estimated constants have been merged with constants obtained previously from medium-resolution spectra for other levels of the X2Π ground state. A self-consistent set of constants is reported for ν′ = 0 and 1 and for ν = 4–9, together with revised equilibrium constants.

Differential cross sections for Ar* scattered by Kr are obtained at four relative kinetic energies, 60.6–156 meV. Location and shape of rainbow maxima, observed at all the energies, are used to determine parameters for a double-Lennard-Jones potential. The parameters, ε=9.11±0.25 meV and rm=5.06±0.84 Å, are the same as those for K+Kr and are substantially different from those of Ar+Kr. A second set of maxima, visible at all energies and caused by exchange of electronic energy from Ar* to Kr, are analyzed to determine electronic-energy exchange cross sections. The cross sections together with those obtained from thermal-energy quenching measurements are consistent with an increase from a threshold of 25 meV. Possible mechanisms for the electronic-energy exchange are discussed.

Differential cross sections for Ar* (3P) scattered by N2(X 1Σg+), obtained at 0.051 eV using crossed molecular beams, are reported from 4° to 174° c.m. A rainbow maximum is observed at 6.3° c.m. The small-angle elastic scattering is analyzed to obtain parameters for a double-Lennard-Jones potential. At large angles the cross sections are depleted by exchange scattering. The exchange probabilities are obtained by subtracting the experimental cross sections from elastic scattering cross sections calculated from the double-Lennard-Jones parameters. The resulting total exchange cross section and threshold energy are σex = 11.8±3.5 Å, E0=0.0081±0.001 eV. Comparison with cross sections deduced from published rate constants indicates that σex increases with initial relative kinetic energy from threshold to 0.051 eV.

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