Anomalies and regularities in the broadening, shifting, and diffusion of D₂ in D₂ and D₂-He mixtures

Precise and accurate measurements of the Q branch lines of D 2 in D 2 and D 2 –He mixtures at several temperatures and low densities reveal a regular broadening at very low densities but only if allowance is made for departures from the soft-collision model. Above about 2 amagat the broadening becomes anomalous and is consistent with earlier observations. Because of the anomalies, a meaningful comparison between broadening and shifting coefficientsand ab initio calculations was not possible. Diffusion constants, as extracted from the data for mixtures, allow us to establish an empirical relation between this diffusion constant and those for pure D 2 and for D 2 infinitely diluted in He.PACS Nos. 33.70Jg and 33.70-W