Resonance Broadening of Homogenous Caesium Vapor in Absorption

The resonance broadening of homogeneous Cs vapor in absorption was studied by means of the contour method. The intensities were obtained via the method of "astigmatic photometry" by utilizing the astigimatism of the Rowland grating. The pressure of the homogeneous absorbing vapor ranged from 10-2 to 17.5 mm Hg. The half breadth varied rather linearly with the number of atoms per unit volume, with γ1/N x 107 = 1.45, γ2/N x 107 = .84 for the 2P3/2 and 2P1/2 components of the resonance lines respectively. The average value of the ratio of half breadths γ1/γ2 was found to be 1.8. The experimental half width γ is found to be about 11/2 times larger than that predicted by Professor Houston. Below pressures of 10 mm Hg the lines exhibited symmetrical broadening according to the "dispersion" formula. At higher pressures indications of a violet and red assymmetry are present for the 2P3/2 and 2P1/2 components respectively. A definite band on the red side of the 2P3/2 and one on the violet side of the 2P1/2 was observed.