Space-charge amplification of the indirect ionization resulting from photoabsorption in cesium vapor has been shown to offer to conventional techniques of absorption spectroscopy a useful complement of highest sensitivity. It was used in this work together with a xenon continuum source filtered to a linewidth of 0.14 Å to measure the relative absorption probabilities for transitions of the cesium-principal-series ($6{}_{}{}^2{}_{}{}^{}S-n{}_{}{}^2{}_{}{}^{}P_{\frac{1}{2},\frac{3}{2}}^{}{}_{}{}^{}$) doublets. Anomalous pressure effects on the resulting line-strength ratios, resulting in part from polarization molecules of ${\mathrm{Cs}}_2$*, were examined over a range of cesium-atom concentration varying from 1.2×${10}^{14}$ to 1.5×${10}^{15}$ ${\mathrm{cm}}^{-3\mathrm{}}$. From the corrected doublet line-strength ratios for $11\le n\le 16$, the segment of the curve of Fano $X$ parameters corresponding to discrete energies was constructed. Interpolation between these results and those from electron-polarization experiments served to locate the pole in the principal-series, doublet line-strength ratio near $19{}_{}{}^2{}_{}{}^{}P$.

• Received 6 May 1974

DOI:https://doi.org/10.1103/PhysRevA.12.1425