Pressure Shifts of the High Terms of the Absorption Series of Na, Rb, and Cs Produced by Hydrogen and Nitrogen

The pressure shifts of the high terms of the principal series of Na, Rb, and Cs produced by commercially pure hydrogen and nitrogen were studied. Measurements were made for different concentrations of the perturbing gases up to a pressure of about 12 atmospheres (617°K) for hydrogen and 7.5 atmospheres (548°K) for nitrogen. The former produced a strong while the latter a very slight violet shift and the effective cross sections as calculated by Fermi's equations were found to be 14.0 ${\mathrm{cm}}^2$/${\mathrm{cm}}^3$, and 2.0 ${\mathrm{cm}}^2$/${\mathrm{cm}}^3$, respectively. For axially symmetrical molecules the values of effective cross sections calculated from Fermi-Reinsberg equations do not agree with those obtained by a direct electrical method.