A calculation of fine-structure transitions in F atoms impinging on both Xe and H+ has been carried out using a novel semiclassical theory that was proposed recently by Miller and George. The theory has the advantage of being conceptually simple and applicable to a wide class of situations. For Xe+F the cross section for the 2P3/2 → 2P1/2 excitation of F rises from its threshold (0.05 eV) to a value of ∼0.1 Å2 at a collision energy of 0.5 eV. The cross section for H++F is much larger, reaching a value of ∼1 Å2 at a collision energy of 0.25 eV, in reasonable agreement with recent quantum mechanical calculations.

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