Experimental study of speed-dependent collisional effects of He and Ne on the 687.1 nm argon line

Using a pressure-scanned Fabry-Perot interferometer precise measurements of the profiles of the 687.1 nm argon line perturbed by helium and neon pressures between 0.5 and 44 torr have been performed. Careful analysis of line shapes showed that for Ar-He the speed-dependent effects do not play any essential role. Contrary to that, for Ar-Ne these effects can give rise to noticeable decrease of the Doppler width determined using the Voigt profile. It was shown that for Ar-Ne the inclusion of speed-dependent effects can reduce the apparent dependence of the Doppler width on the neon density and cause the Doppler temperatures determined from the profiles to be consistent with the source temperature. The role of the Dicke narrowing is also discussed.