Photodetachment total cross sections

The total photodetachment cross section describes the probability that an electron is detached from a negative ion following the absorption of a photon, regardless the excitation state of the residual atom or the energy or direction of the emitted electron. A total cross section is the sum of partial cross sections for detachment into each of the energetically allowed continua. This is illustrated in Fig. 1. Here we show the three possible channels accessible to a doubly excited state of Li" that lies just below the Li(32P) detachment threshold. The total cross section may be determined by... 

Fig. 3 Yield of Li atoms vs. photon energy in the range 4.2-4.5 eV. The Li signal is proportional to the total cross section for the photodetachment of Li via the 2 Skp, 2 Pks,d and 3 Skp channels (see Fig. 1). The experimental data (dots) has been normalized to theory (solid line with scale to the right) at the 3 P threshold.

C. Sinanis, Y. Komninos, and C. A. Nicolaides, Asymmetry parameter and total cross section for the photodetachment of the metastable Be ls 2s2p state, Phys. Rev. A, 51(4), R2672-R2675 (1995). 

We present the results of experimental studies of photon-negative ion interactions involving the dynamics of two electrons. Resonances associated with doubly excited states of Li and He" have been observed using laser photodetachment spectroscopy. Total and partial photodetachment cross sections have been investigated. In the former case, the residual atoms are detected irrespective of their excitation state, while in the latter case only those atoms in specific states are detected. This was achieved by the use of a state selective detection scheme based on the resonant ionization of the residual atoms. In addition, in the case of Li-photodetachment, the threshold behavior of the Li(2 P)+e-(ks) partial cross section has been used to accurately measure the electron affinity of Li. 

Although the abovementioned theories were formulated in the context of either photoionization of atoms or electron scattering with atoms, they lend themselves equally well to photodetachment of negative ions, where an essential question is again to construct the wavefunction for the total continuum state in the presence of transient states embedded in continua. The main results from Mies s work [54] for calculating cross sections are summarized below. 

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