Single-center approach for photodetachment and radiative electron attachment: Comparison with other theoretical approaches and with experimental photodetachment data

A single-center method for calculating photodetachment cross section for anions and radiative electron attachment cross section for neutral molecules by microreversibility is presented. It uses the integral equation method to calculate the ejected electron's continuum wave function while the single-electron bound function of the anion is described by the Dyson orbital. It is compared with related theoretical approaches and benchmarked to the experimental photodetachment cross sections of ${{\mathrm{O}}_2}^{-}$, ${\mathrm{OH}}^{-}$, and ${\mathrm{CN}}^{-}$. The use of the plane-wave approximation of the ejected electron wave function combined with the Hartree-Fock frozen-core approximation of the Dyson orbital is also considered and its results are compared with those of our methods and with experiment. A good agreement between the calculated photodetachment cross sections and the experimental data is obtained for ${{\mathrm{O}}_2}^{-}$ and ${\mathrm{CN}}^{-}$ when using the three methods. For ${\mathrm{OH}}^{-}$, the calculated scattering-wave electron photodetachment cross sections agree well with two most recent sets of experimental data among the three available while the plane-wave results disagree with all the experimental and theoretical data. The different approaches to calculate the Dyson orbital are also discussed as well as the convergence of the calculations with respect to the choice of the one-electron basis set. The approximation of Dyson orbitals by Kohn-Sham orbitals appears to overestimate the photodetachment cross section.

Figure 1

Experimental [59, 60] and calculated EPD cross section of ${{\mathrm{O}}_2}^{-}$. The calculated cross sections correspond to the different representations of the electron continuum wave function: plane wave (PW), scattered wave using a separable exchange potential (SEPEX), scattered wave using Hara's free-electron-gas exchange potential (HFEGE). The dotted red line shows the PW cross section of Oana et al. [45].

Figure 2

Experimental [53, 61, 62, 63] and calculated EPD cross section of ${\mathrm{OH}}^{-}$. Notation as in Fig. 1.

Figure 3

$\mathrm{\Lambda }$ components of the EPD cross section of ${\mathrm{OH}}^{-}$.

Figure 4

Experimental [65] and calculated EPD cross section of ${\mathrm{CN}}^{-}$. The cyan area corresponds to the $R$-matrix calculations of Khamesian et al. [13]. The dotted red line shows the PW calculation of Skomorowski et al. [20]. Notation as in Fig. 1.

Figure 5

Calculated REA cross section of ${\mathrm{CN}}^{-}$. The cyan area corresponds to the $R$-matrix calculations of Khamesian et al. [13]. The dotted red line corresponds to the Kohn variational principle calculations of Douguet et al. [28]. Notation as in Fig. 1.

Figure 6

Plane-wave EPD cross sections for different approaches to the calculation of the Dyson orbital.

Figure 7

Plane-wave EPD cross sections for different one-electron basis set employed in the CASSCF calculations of the Dyson orbital.

Figure 8

Plane-wave REA cross section for different basis set employed in the CASSCF calculation of the Dyson orbital.