Pressure Broadening of the Blue Cesium Doublet Produced by Argon and Helium†

The shift and broadening of the second member of the principal series of cesium produced by argon and helium were observed for pressures up to 170 and 90 atmospheres, respectively. The shift produced by argon was linear throughout the entire range of relative densities and was nearly the same for both doublet components. The average slope was 2.7 cm−1/relative density with the short-wavelength component ( P232) having a slightly higher value. For helium the shift obeyed a linear relationship for relative densities above 8 and 16 with slopes of 3.5 and 4.4 cm−1/relative density for the P212 and the P232 components, respectively. The broadening for both lines in the case of argon appeared to be linear up to a relative density of 45 beyond which there was a marked increase in slope, changing from 2.0 to 5.1 cm−1/relative density. The broadening of the P232 component was consistently higher than that of the P212 component. For helium the P212 component was broadened more than the P232 component at relative densities less than 12.5. Beyond this value the broadening of the P232 component was considerably higher.