Total inelastic cross sections for potassium ion–atom collisions: Oscillations in the velocity dependence and correlation with molecular structure

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Abstract
Electronic excitation leading to light emission in the wavelength range 350–800 nm has been studied by a crossed ion–atom beam technique for (K+, K) collisions, and the results are interpreted in terms of properties of the potential energy curves for the molecular ion K+2. The investigated velocity range is (1.3–12) ×106 cm s−1. The total cross section for the process K+(3p6 1S0) +K(4s 2S1/2) →K+(3p6 1S0) +K(4p 2P3/2,1/2) increases from threshold up to ∼10−15 cm2 at a velocity of ∼4.5×106 cm s−1, and shows an oscillatory structure. The magnitude and over‐all velocity dependence are attributed to a Σ–Π curve crossing, and the oscillations to an interference effect, which is treated as an inelastic ’’glory’’ phenomenon. Cross sections for production of each of the fine structure components of K(4p), 2P3/2, and 2P1/2, have also been measured. Their ratio, which in the investigated velocity range is different from the statistical value, shows additional oscillations, which are discussed in terms of long range interference between alternate semiclassical paths.