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We study the process of laser-assisted spontaneous electron bremsstrahlung by running classical trajectories in a combined Coulomb and laser (ac) fields. Due to chaotic scattering in the combined Coulomb and ac fields, the radiation probability as a function of the impact parameter and the constant phase of the laser field exhibits fractal structures. However, these structures are smeared out when the cross section is integrated over the impact parameter and averaged over the phase. We analyze the role of different types of orbits, including the trapped orbits, and the dependence of the radiation probability on the impact parameter and the initial phase of the ac field.We show that, at low incident electron kinetic energy, the Coulomb focusing leads to a substantial extension of the range of impact parameters contributing to the bremsstrahlung cross section and results in a substantial increase (by one to two orders of magnitude) of the cross section as compared with the pure Coulomb case. As examples, we discuss the case of relatively high ponderomotive energy Ep when we obtain an efficient production of photons with frequencies up to 2Ep, and the case of low Ep when only infrared photons are produced. Overall accuracy of the classical approach is estimated to be very good, although it does not describe resonant processes studied previously by quantum-mechanical methods.
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Laser-assisted radiative recombination in a cold hydrogen plasma
Abstract We study the process of laser-assisted radiative recombination of an electron with a proton in a cold hydrogen plasma employing the semiclassical Kramers’ approach which involves calculation of classical trajectories in combined laser and Coulomb fields and the use of the correspondence principle. Due to the Coulomb focusing effect, recombination is the most effective when the initial electron momentum is parallel to the laser polarization. Orders of magnitude enhancement of the cross section, as compared to the laser-free case, is observed in this case. With increasing angle between the electron momentum and polarization, the recombination cross section drops. However, even after averaging over Maxwellian velocity distribution we obtain a substantial enhancement of the recombination rate constant, as compared to the zero-field case. For the field intensities in the range 30–350 MW cm−2, the enhancement occurs in the region of the radiation wavelength from 5 to 20µm and for the plasma temperature from 20 to 300 K.
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- Award ID(s):
- 2309261
- PAR ID:
- 10541176
- Publisher / Repository:
- IOP Publishing
- Date Published:
- Journal Name:
- Journal of Physics B: Atomic, Molecular and Optical Physics
- Volume:
- 57
- Issue:
- 19
- ISSN:
- 0953-4075
- Format(s):
- Medium: X Size: Article No. 195201
- Size(s):
- Article No. 195201
- Sponsoring Org:
- National Science Foundation
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