Schwingungsrelaxation von CO₂ in Gemischen mit Helium

Abstract

The excitation mechanisms of the vibrational degrees of freedom of CO₂ in gaseous mixtures with 0–99 per cent helium have been studied by acoustic absorption measurements. It turns out that the excitation always occurs in binary collisions, in which helium as collision partner is 22 times more efficient than CO₂ itself. A monotonic increase of the relaxing part of the specific heat with increasing helium content, in excess of the total vibrational specific heat of the mixture, can be explained as influence of simultaneous rotational-vibrational transitions. Hereby those transitions, in which the vibrational and rotational energy of a CO₂ molecule changes oppositely, are more frequent than those with like energy changes.