Theory of two-atom coherence in gases. II. Continuous-wave spectra

Abraham Ben-Reuven
Phys. Rev. A 22, 2585 – Published 1 December 1980
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Abstract

General expressions are derived for the spectral line shapes of resonance absorption and scattering of coherent radiation in collision-broadened gases, taking into account effects of coherent excitation of two or more atoms (or molecules), as steady-state solutions of a hierarchy of master equations described in a previous publication (paper I). Coupling between the coherent motions of the atoms, provided by a Bethe-Salpeter—type effective interaction, in the binary-collision approximation, forms the essential mechanism for introducing cooperative coherent effects into the steady-state spectra. Explicit expressions are given for the effects of two-atom coherence in the binary-collision approximation, in which the Bloch-type dressed-atom self-energy superoperator is modified by the presence of collisions in which both atoms retain memory of their coherent propagation before the collision. The self-energies include the effects of resonance exchange symmetrization in self-broadening, and are renormalized by the coincidence of radiative transitions during the collisions. The impact (near-resonance) and the quasistatic (line-wing) limits of the applied-frequency detunings are discussed. In the quasistatic limit, coherent many-atom excitations become irrelevant; however, interactions of both collision partners with the radiation during the collision accounts for such phenomena as collision-induced absorption or radiative collisions. In the impact limit, the inclusion of the Bethe-Salpeter interactions allows for the appearance of two-atom resonances. Magnitude estimates of these effects are discussed. Effects of higher-rank (many-body) coherences are formally discussed with the help of a diagrammatic method, leading into implicit bootstrap equations that can be solved by iterative or other procedures.

  • Received 14 April 1980

DOI:https://doi.org/10.1103/PhysRevA.22.2585

©1980 American Physical Society

Authors & Affiliations

Abraham Ben-Reuven*

  • Joint Institute for Laboratory Astrophysics, National Bureau of Standards and University of Colorado, Boulder, Colorado 80309

  • *Visitor at JILA, 1979-1980, on leave from the Institute of Chemistry, Tel Aviv University, Tel Aviv, Israel.

See Also

Theory of two-atom coherence in gases. I. Master equations

Abraham Ben-Reuven
Phys. Rev. A 22, 2572 (1980)

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Vol. 22, Iss. 6 — December 1980

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