Pressure Effects of Rare Gases on the Absorption Line Ca4227. I. The Effects of Argon and Helium

The shift, broadening, and line shape of the absorption line Ca 4227 in the presence of Ar and He were observed under a wide range of pressures. The relative densities (rd) employed extended from 1 to about 245 (15 450 psi at 638 °C) for Ar and to 58 (2563 psi at 638 °C) for He. Both Ar and He produce a red shift, -0.019 ${\mathrm{cm}}^{-1\mathrm{}}$/rd for He and -0.023 ${\mathrm{cm}}^{-1\mathrm{}}$/rd for Ar. The dependence of the half-width on rd appears to adhere to linearity less than does the dependence of the shift on the rd. The broadening at low rd (<10) is 0.64 ${\mathrm{cm}}^{-1\mathrm{}}$/rd for He and 0.74 ${\mathrm{cm}}^{-1\mathrm{}}$/rd for Ar. Some typical intensity profiles are given showing also the presence of a very extended blue wing due to He and a broad violet satellite due to Ar.