Theoretical premises for experimental verification of the deviations from the wannier threshold behaviour

Abstract

Abstract. The Wannier [13 theory describes the escape of two electrons from a charged core in the threshold domain. Its modification [3] is applied to some features of the double escape processes which were not analyzed previously in due extent. The behaviour of the total cross sections for a small, but finite, energy excess E above the threshold is described incorporating the deviations from the well known Wannier power law. The processes with the escape of electron and positron from the core are also considered. The energy dependence of the spin asymmetry A in (e, 2e) collisions is analyzed in connection with the recent experimental data (which seem to manifest some dependence A(E) in the near-threshold domain contrary to the conventional Wannier theory). The theory suggests the requirements for the accuracy of the experiments intended to verify the Wannier threshold laws and detect the deviations from them.

Threshold laws for the breakup of atomic particles into several charged fragments

“…Being based on an appealing mechanism, it has inspired a large number of studies where the law was rederived, extended, tested or rebutted. The intensity of these studies does not show a decrease with time as testify some representative references to the recent publications [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21]. A complete bibliography on the subject would be immense.…”

“…Our treatment generalizes to multimode case the scheme developed by Kazansky and Ostrovsky [4] for the two-electron escape (see also Ref. [12]; some of ideas used were elaborated also by Watanabe [2]). Note that the cited paper [4] provides also a description of deviations from pure power threshold law, but we do not pursue this point here.…”

“…Still, we can note that for the electron-impact ionization of atoms or for double photoionization this domain is limited to few eV above threshold (for quantitative treatment within the Wannier mechanism see Refs. [4] [12]). For the positronimpact ionization the applicability domain is even less [12] [13].…”

“…They are quantized following a general scheme suggested by Kazansky and Ostrovsky [34] [35]. This allows us to construct a reduced form of the wave function for the system of charged particles and derive the threshold law in Section IV generalizing a procedure used previously by Kazansky and Ostrovsky [4] [12] for derivation of the conventional Wannier law. Application of a developed general scheme to some particular systems (Section V) is followed by concluding discussion of special features of the Wannier-type threshold laws, with an emphasis on a relation between the underlying statistical and dynamical aspects of the problem (Section VI).…”

Threshold Law For Positron Impact Ionization of Atoms

“…We also find the energy range over which the Wannier power law is valid. (See also [5].) The threshold behavior of the cross section for positron impact ionization is a much more sensitive test for threeparticle correlations than electron impact ionization.…”