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 D2 in D2 and D2-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 coefficients and 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 D2 and for D2 infinitely diluted in He.