Cross sections and photoelectron angular distributions in photodetachment from negative ions using equation-of-motion coupled-cluster Dyson orbitals

We report total and differential cross sections for photodetachment from negative ions using Dyson orbitals calculated from equation-of-motion coupled-cluster wave functions and free wave description of the detached electron. The energy dependence of the cross sections is reproduced well, however, the accuracy of absolute values varies. For F-, C-, NH2-, and H-, the calculated cross sections are within the error bars from the experimental values, whereas the errors for Li- and OH- are about 20%. The largest errors are observed for O- and O-2(-) for which the calculated cross sections differ from the experimental ones by factors of 3 and 2, respectively. Calculated anisotropy parameters for atomic anions exhibit too slow decrease, which suggests that the diffuseness of the computed Dyson orbitals is underestimated. Moreover, in the asymptotic region, the orbitals exhibit artifactual oscillations probably due to the limitations of Gaussian basis sets. The analysis of the trends in the experimental anisotropy parameters suggests that the interaction of the detached electron with the core, which is neglected in the present model, is important. (C) 2009 American Institute of Physics. [doi:10.1063/1.3231143]