Pressure Effects of Rare Gases on the Second Doublet of Rubidium Principal Series

The displacement, asymmetry, and broadening of the second doublet of the rubidium principal series perturbed by pure helium, neon and argon up to 13 atmospheres are observed. The displacement as well as the broadening of the doublet components are not the same. The ${}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}$ component shifts and broadens more conspicuously than the ${}_{}{}^2{}_{}{}^{}P_{1\frac{1}{2}}^{}{}_{}{}^{}$ component (an exception being the broadening by argon). The departure from linear relationship between the shift and the density of the perturbing gas is quite manifest. Both for helium and for neon the line contour shows a distinct asymmetry towards the violet, while for argon the line contour shows a very strong red asymmetry. For helium and neon the violet asymmetries of the ${}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}$ component are stronger than that of the ${}_{}{}^2{}_{}{}^{}P_{1\frac{1}{2}}^{}{}_{}{}^{}$ component; the reverse is true for argon. The relationship between the half-width and the relative density is linear for foreign gas concentrations of relative densities up to 8 so far applied.