Broadening and shift of the sodium diffuse series by noble gas

The impact broadening due to He, Ne, Ar, Kr, and Xe of the Na $3p{}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}-4d{}_{}{}^2{}_{}{}^{}D_{\frac{3}{2}}^{}{}_{}{}^{}$ (5683 Å) line has been measured at a temperature of 500 °K. In addition, impact shifts of this line and other diffuse series lines up to the transitions from $6d{}_{}{}^2{}_{}{}^{}D$ have also been determined. The observed broadening and shift rates are in agreement with Lindholm-Foley calculations using semiempirical alkali-metal-noble-gas potentials reported previously. A comparison of calculated and observed shifts show that alkali-metal-helium potentials are somewhat more repulsive than previously thought, and also that the collision-averaged potentials corresponding to $3p{}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}$ are less attractive than those for $3p{}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}$. We conclude that the use of these potentials in the impact approximation will predict the broadening and shift of alkali-metal spectral lines by noble gases with an accuracy of 10-20%.