Example: photodetachment of an electron from a negative ion

Photodetachment of an electron from a negative ion plays important role in a number of issues of the physics of radiative-matter interaction. Together with radiative attachment photodetachment participates in the establishment of the plasma equilibrium. This process is the inverse one to the radiative attachment of an electron to atomic hydrogen. The latter is the key mechanism of the formation of the Sun spectrum in visible and near-infrared range.

Calculation of the photodetachment cross section is facilitated by the fact that ejected electron moves in the screened field of neutral atom. Therefore the wave function of this electron can be described in plane wave approximation. Thus the photodetachment cross section with reasonable accuracy can be expressed in terms of Fourier transform of radial wave function of core subshell. This wave function is taken as Slater decomposition of Hartree-Fock solution of corresponding Schrodinger equation with tabulated coefficients. In the case of atom with high polarizability the polarization effects should be taken into account in the calculation of photodetachment cross section. These effects mean that actual field inducing photodetachment is a sum of external radiation field and the field due to the polarization of the atomic core by the radiation. The figure below demonstrates the role of polarization effects in the electron photodetachment from negative lithium ion. Presented cross sections are calculated in the frame of the first order of perturbation theory. One can see that there is the destructive interference between external field and polarization field which leads to the decrease of the total photodetachment cross section.  

Photodetachment cross section for negative lithium ion calculated with account for core polarization (black curve) and without such account (red curve).

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