Electron–Positron Pair Production in Superstrong Laser Fields

Abstract

Considering the interaction of charged particles with strong radiation fields in vacuum, we looked at the non-quantum electrodynamic (QED) properties of electromagnetic vacuum. At such consideration, vacuum stipulates only the classical dispersion properties of EM waves propagating with the speed of light c. However, the latter is valid for radiation fields that are not superstrong \((\xi _{0} 1\) the energy acquired by an electron over a wavelength of a coherent radiation field exceeds the electron rest energy \(mc^{2}\). On the other hand, the energetic width of the vacuum gap or the threshold value for the electron–positron pair production is \(2mc^{2}\). This means that electrons of the Dirac vacuum acquiring the energy \(\mathcal {E}> 2mc^{2}\) at the interaction with the wave field of intensity \(\xi _{0}>1\) will pass from negative-energy states to positive ones (excitation of the Dirac vacuum) and electron–positron pair production becomes a fact (with the presence of a third body for the satisfaction of the conservation laws for this process). The production of electron–positron pairs by plane EM waves of relativistic intensities (\(\xi _{0}\gg 1\)) is essentially a multiphoton process, which principally differs from the known “Klein paradox” —production of electron–positron pairs in stationary and homogeneous electric field proceeding over the electron Compton wavelength. The latter corresponds to the tunnel effect through the effective energetic barrier of finite width formed from the vacuum gap of infinite width by the presence of a uniform electric field (Schwinger mechanism). The physical mechanisms are similar to two different limits of the above-threshold ionization of atoms in strong radiation fields—multiphoton and tunnel ionization. This chapter considers the excitation of the Dirac vacuum in superstrong EM fields and the electron–positron pair production process in the presence of a diverse-type third body.