Photodetachment ofK−andRb−to the lowest-lyingS122,P122, andP322states of K and Rb

A crossed-ion-beam-laser apparatus has been used to measure the branching ratios for photodetachment of ${\mathrm{K}}^{-}$ and ${\mathrm{Rb}}^{-}$ ions to the lowest-lying ${}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}$, ${}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}$, and ${}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}$ states of the resulting neutral atoms as a function of photon energy between the thresholds for producing the excited-state atoms and up to 50 meV beyond. The branching ratios are determined by measuring the total neutral-atom production and the excited-state to ground-state decay radiations. Between thresholds, the results are in good agreement with the ${\mathrm{K}}^{-}$ results of Slater and the ${\mathrm{Rb}}^{-}$ results of Frey Above the ${}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}$ threshold, our ${\mathrm{K}}^{-}$ results quickly approach constant values and do not show the energy-dependent structure observed by Falk, Leep, and Geballe. The angular distributions of the ${}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}$ decay radiations have been measured and are found to agree in magnitude with calculated expectations and to be independent of energy over the range of observation. The polarization-based multichannel quantum-defect theory of Watanabe and Greene has been fitted to the ${\mathrm{K}}^{-}$ results of Slater and the ${\mathrm{Rb}}^{-}$ results of Frey Our measurements are in agreement with these calculations.