Single- and Double-Quantum Photodetachment of Negative Ions

The recent measurement of the transition probability for the double-quantum detachment of an electron from ${\mathrm{I}}^{-}$ has prompted a new theoretical study of this problem. A central-field model for bound and free states is used, in which a parameter is adjusted in the potential to yield the observed binding energies of the negative ions. An implicit-sum method, requiring the solution of inhomogeneous radial equations, is used to evaluate the sums over intermediate states. The results for ${\mathrm{I}}^{-}$ lie almost within the experimental uncertainty. The cross sections for single-quantum photodetachment and electron elastic scattering (from the neutral atom) are also given for the ions studied: ${\mathrm{C}}^{-}$, ${\mathrm{O}}^{-}$, ${\mathrm{F}}^{-}$, ${\mathrm{Si}}^{-}$, ${\mathrm{S}}^{-}$, ${\mathrm{Cl}}^{-}$, ${\mathrm{Br}}^{-}$, ${\mathrm{I}}^{-}$.