Collisional redistribution of fluorescence radiation

doi:10.1016/0378-4363(77)90138-3

Physica B+C

Volume 92, Issue 3, November–December 1977, Pages 397-408

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Abstract

We derive a general quantum-mechanical expression for the spectral distribution of resonance fluorescence of an atom in a perturber gas, excited by a monochromatic polarized non-saturating light source. The Doppler effect is included and we avoid the restrictions of the impact limit. We specialize the equations to the simple case of non-degenerate states in order to obtain an expression for the redistribution function in terms of the ordinary line profile as measured in absorption and of the corresponding dispersion function. We study the case of far-wing excitation and we show that the results match the experimental observations reported by Carlsten and Szöke.

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The principles and applications of the quasimolecular treatment of optical and radiative collisions are discussed. Main attention is focused on the uniform approximation to the unified Franck-Condon (UFC) line shape of near- and far-wings and of rainbow satellites associated with pressure-broadened spectral lines, on radiative-collision cross-sections, and on collisional redistribution of radiation. In the review of experimental data the emphasis is placed upon those results which test theoretical predictions and knowledge of the interactions.
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A previously published semiclassical formulation of the atomic line profile coefficients in terms of generalized redistribution functions is made more explicit by deriving atomic redistribution functions for three-photon processes. Quantum mechanical calculations are carried out for a general three-photon process corresponding to the atomic transition sequence i → j → k → f, for nondegenerate states i, j, k, f and within the framework of the impact approximation. For comparison, analogous calculations are also performed using the substate (Weisskopf-Woolley) picture. It is Found that the quantum mechanical and the substate forms of generalized redistribution functions agree in the limit of no collisions, whereas in the presence of collisions they agree only if level interface phenomena of the collisional line broadening are negligible. The physical assumption underlying the substate picture are discussed in detail.
Saturated two-photon absorption by calcium atoms in a perturber bath
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Collisional redistribution of radiation
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Collisional redistribution of fluorescence radiation

Abstract

Physica

Physica

Physica

Phys. Rep.

Astrophys. J.

Phys. Rev. Lett.