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Physical Review A

Electron-impact excitation of a metastable hydrogen atom in the presence of a resonant laser field

S. P. Purohit, K. C. Mathur

Published May 1, 1992• 8 citations
Publisher

Abstract

Electron-impact excitation of the hydrogen metastable 2s state to the 3s, 4s, 3d, and 4d states is studied in the presence of a resonant laser field using the rotating-wave approximation. The frequency of the circularly polarized laser field is chosen to match the 2s-3p transition frequency in the hydrogen atom. The role of the laser field in individual magnetic substate (${\mathit{m}}_{\mathit{f}}$=0,\ifmmode\pm\else\textpm\fi{}1,\ifmmode\pm\else\textpm\fi{}2) excitation is analyzed. It is found that for these optically forbidden transitions (s-s, s-d), a significant increase in the excitation cross sections is obtained through joint collisions with electrons and photons.

DOI
10.1103/physreva.45.6502

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H(3s) beam production by laser excitation of metastable hydrogen atoms in an electric field. II. Theoretical approach

D. Fussen, W. Claeys, A Cornet +1 more

For pt.I see ibid., vol.18, no.18, p.3557-37 (1985). A quantitative description of H(3s) atoms produced by laser excitation of a metastable hydrogen beam in an electric field is performed and compared with the recent experimental results of Claeys et al. (1985). The Stark effect for n=3 is calculated to obtain the relative intensities of the five Stark transitions as a function of the field strength. Good agreement with the experimental values is found. The dynamical behaviour of the 3s and 3p Stark states when the atoms leave the field is then analysed. Due to the adiabatic evolution we found that only one Stark state can produce H(3s) atoms.

Journal of Physics B Atomic and Molecular Physics•Sep 28, 1985•7 citations
Electron-impact excitation of the hydrogen metastable 2s state to the 3s, 4s, 3d, and 4d states is studied in the presence of a resonant laser field using the rotating-wave approximation. The frequency of the circularly polarized laser field is chosen to match the 2s-3p transition frequency in the hydrogen atom. The role of the laser field in individual magnetic substate (mf{\mathit{m}}_{\mathit{f}}mf​=0,\ifmmode\pm\else\textpm\fi{}1,\ifmmode\pm\else\textpm\fi{}2) excitation is analyzed. It is found that for these optically forbidden transitions (s-s, s-d), a significant increase in the excitation cross sections is obtained through joint collisions with electrons and photons.
High-energy cross sections for the excitation of the 3s state of the hydrogen atom by simultaneous collision with electrons and photons are calculated under the second-order Bethe-Born approximation, both as functions of electron energy and of laser intensity. Resonant structures are shown to arise as a function of laser-photon frequency. The behaviour of these resonances is described and their origin explained. It is concluded that these resonances are characteristic of the simultaneous electron-photon excitation process itself and can occur for any atomic target, under suitable conditions.
The collision of a proton with a hydrogen atom in the presence of electromagnetic radiation which is nearly resonant with the atomic levels is investigated theoretically. The non-perturbative quasi energy method is used to describe the laser-atom interaction and the proton-dressed atom collision is solved using a diagonalization technique. We have calculated the transition probabilities and the total cross-section for various transitions. We discuss the influence of various laser and collision parameters on the excitation process.
For pt.I see ibid., vol.18, no.18, p.3557-37 (1985). A quantitative description of H(3s) atoms produced by laser excitation of a metastable hydrogen beam in an electric field is performed and compared with the recent experimental results of Claeys et al. (1985). The Stark effect for n=3 is calculated to obtain the relative intensities of the five Stark transitions as a function of the field strength. Good agreement with the experimental values is found. The dynamical behaviour of the 3s and 3p Stark states when the atoms leave the field is then analysed. Due to the adiabatic evolution we found that only one Stark state can produce H(3s) atoms.