Near-resonant V-V energy transfers between CO₂(00⁰1) and SiF₄ and SF₆, at temperatures below 300 K

The variations with temperature of near-resonant (V-V) deexcitation cross sections for CO₂(00⁰1) + SiF₄ and CO₂(00⁰1) + SF₆ were determined for 300 < T/K < 210, for two sets of compositions. Whereas previous experiments and theoretical models agreed that for T > 300 K σ increases proportional to T^-1, for several collision partners, the present values show a clear decrease of the cross sections from linear dependence on T^-1. Indeed, it appears that σ values pass through a shallow maximum in the vicinity of T ≈ 250 K.