Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Physical Review A

Two-photon collisional redistribution of radiation

G. Alber, J. Cooper

Published Jun 1, 1985• 15 citations
Publisher

Abstract

We study collisional redistribution in the presence of two weakly exciting laser fields, including the effects due to degeneracy of the radiator states. A general expression for the total redistributed intensity is derived valid for arbitrary detunings and polarizations of the exciting laser fields. In particular, this expression contains all single- and sequential-collisional contributions, which are equally important under certain circumstances. We also point out the similarities and differences between the redistributed intensity as calculated in this paper and collisionally aided radiative excitation cross sections, which have been studied previously.

DOI
10.1103/physreva.31.3644

Related papers

Intensity effects in two-photon collisional redistribution of radiation

G. Alber, J. Cooper

We study laser-intensity effects in two-photon collisional redistribution of radiation. Thereby we concentrate on a special case of recent experimental interest, where the transition from the excited to the final state is saturated by a strong laser field. Both exciting lasers are, however, assumed weak in the sense that the dynamics of a collision between the radiator and a perturber is not significantly influenced by the laser fields. In particular, our treatment explains the intensity independence of the polarization dependence of total fluorescence from the final state which has been measured previously even if the transition from the excited to the final state is saturated.

Physical Review A•Oct 1, 1985•2 citations

Collisional redistribution of radiation. II. The effects of degeneracy on the equations of motion for the density matrix

Keith R. Burnett, J. Cooper

We apply the analysis of paper I to degenerate atomic systems and calculate the effect of correlations between an atom (the absorber) and perturbers in the binary-collision approximation. The result of our calculation is a generalized absorption profile that specifies the final state of the atom an absorption event. This profile is then related to the total intensities of Rayleigh scattering and fluorescence (redistributed radiation) from the atom. The profile is expressed in terms of collision operators that depend on the index of the multipole of the atom that is created. Some of the operators represent correlations between radiative and collisional events and cannot, except in certain limits, be expressed in terms of the usual line-broadening operators. This, of course, implies that one needs extra dynamical information, on top of that obtainable from ordinary absorption experiments, to be able to describe redistribution. Conversely, redistribution offers a probe of collisional dynamics, not given by absorption experiments, via the polarization of fluorescent light. We give practical expressions for the calculation of these operators and discuss their implications.

Physical Review A•Nov 1, 1980•65 citations

Optical collisions and saturated radiative transition rates

Gerard Nienhuis

The formal structure of the time dependence of the state of an atom in a perturber bath in an intense classical monochromatic radiation field is studied. The authors allow the cross sections of binary collisions to be affected by the radiation field. The result is used to derive an expression for the collision-broadened saturated fluorescence excitation spectrum and absorption rate in terms of a collisional relaxation operator. This operator can be related to the rate of collisionally aided radiative excitation.

Journal of Physics B Atomic and Molecular Physics•Sep 14, 1981•23 citations

Collisional redistribution of radiation. II - The effects of degeneracy on the equations of motion for the density matrix. III - The equation of motion for the correlation function and the scattered spectrum

Keith R. Burnett, J. Cooper

The effect of correlations between an absorber atom and perturbers in the binary-collision approximation are applied to degenerate atomic systems. A generalized absorption profile which specifies the final state of the atom after an absorption event is related to the total intensities of Rayleigh scattering and fluorescence from the atom. It is suggested that additional dynamical information to that obtainable from ordinary absorption experiments is required in order to describe redistributed atomic radiation. The scattering of monochromatic radiation by a degenerate atom is computed in a binary-collision approximation; an equation of motion is derived for the correlation function which is valid outside the quantum-regression regime. Solutions are given for the weak-field conditions in terms of generalized absorption and emission profiles that depend on the indices of the atomic multipoles.

Physical Review A•Nov 1, 1980•0 citations

Collisional redistribution of radiation. I. The density matrix

Keith R. Burnett, J. Cooper, R. J. Ballagh +1 more

As a first step in deriving accurate, calculable expressions for collisional redistribution of radiation, valid outside the impact regime, we present a method for calculating an accurate binary-collision density operator for an atom in the presence of a driving field and perturbers. We use projection-operator techniques to establish first the precise validity of the Markoff approximation for radiative relaxation. Using the same techniques, we show how the collisional-relaxation problem may be analyzed in a practical manner outside the Markoff approximation. The effect of correlations between radiative and collisional events is included in a consistent way, and the physical implications of these correlation effects are demonstrated for a simple example, the two-level atom with nondegenerate levels.

Physical Review A•Nov 1, 1980•96 citations

Calculations on laser-induced collisional energy transfer

S. Geltman

We examine theoretically the behavior of cross sections for laser-induced collisional energy transfer (LICET) over a wide range of detunings and laser intensities for the two-atom pairs Li-Sr and Eu-Sr which have been previously studied experimentally. These two cases are complementary in that the laser and collisional interactions enter in opposite orders, and their level structures are such as to give weak-field line shapes of opposite asymmetry and intensity shift. A three-state model is used and the Bambini-Berman formula for the weak-field quasistatic wing is verified. At high intensities the peak cross section is found to go through a maximum and the LICET profile is found to become symmetric about a shifted center with notable departures from a uniform falloff in the far quasistatic wing, apparently arising from radiative collisional interference effects.

Physical Review A•Apr 1, 1992•21 citations
We study collisional redistribution in the presence of two weakly exciting laser fields, including the effects due to degeneracy of the radiator states. A general expression for the total redistributed intensity is derived valid for arbitrary detunings and polarizations of the exciting laser fields. In particular, this expression contains all single- and sequential-collisional contributions, which are equally important under certain circumstances. We also point out the similarities and differences between the redistributed intensity as calculated in this paper and collisionally aided radiative excitation cross sections, which have been studied previously.
We study laser-intensity effects in two-photon collisional redistribution of radiation. Thereby we concentrate on a special case of recent experimental interest, where the transition from the excited to the final state is saturated by a strong laser field. Both exciting lasers are, however, assumed weak in the sense that the dynamics of a collision between the radiator and a perturber is not significantly influenced by the laser fields. In particular, our treatment explains the intensity independence of the polarization dependence of total fluorescence from the final state which has been measured previously even if the transition from the excited to the final state is saturated.
We apply the analysis of paper I to degenerate atomic systems and calculate the effect of correlations between an atom (the absorber) and perturbers in the binary-collision approximation. The result of our calculation is a generalized absorption profile that specifies the final state of the atom an absorption event. This profile is then related to the total intensities of Rayleigh scattering and fluorescence (redistributed radiation) from the atom. The profile is expressed in terms of collision operators that depend on the index of the multipole of the atom that is created. Some of the operators represent correlations between radiative and collisional events and cannot, except in certain limits, be expressed in terms of the usual line-broadening operators. This, of course, implies that one needs extra dynamical information, on top of that obtainable from ordinary absorption experiments, to be able to describe redistribution. Conversely, redistribution offers a probe of collisional dynamics, not given by absorption experiments, via the polarization of fluorescent light. We give practical expressions for the calculation of these operators and discuss their implications.
The formal structure of the time dependence of the state of an atom in a perturber bath in an intense classical monochromatic radiation field is studied. The authors allow the cross sections of binary collisions to be affected by the radiation field. The result is used to derive an expression for the collision-broadened saturated fluorescence excitation spectrum and absorption rate in terms of a collisional relaxation operator. This operator can be related to the rate of collisionally aided radiative excitation.
The effect of correlations between an absorber atom and perturbers in the binary-collision approximation are applied to degenerate atomic systems. A generalized absorption profile which specifies the final state of the atom after an absorption event is related to the total intensities of Rayleigh scattering and fluorescence from the atom. It is suggested that additional dynamical information to that obtainable from ordinary absorption experiments is required in order to describe redistributed atomic radiation. The scattering of monochromatic radiation by a degenerate atom is computed in a binary-collision approximation; an equation of motion is derived for the correlation function which is valid outside the quantum-regression regime. Solutions are given for the weak-field conditions in terms of generalized absorption and emission profiles that depend on the indices of the atomic multipoles.
As a first step in deriving accurate, calculable expressions for collisional redistribution of radiation, valid outside the impact regime, we present a method for calculating an accurate binary-collision density operator for an atom in the presence of a driving field and perturbers. We use projection-operator techniques to establish first the precise validity of the Markoff approximation for radiative relaxation. Using the same techniques, we show how the collisional-relaxation problem may be analyzed in a practical manner outside the Markoff approximation. The effect of correlations between radiative and collisional events is included in a consistent way, and the physical implications of these correlation effects are demonstrated for a simple example, the two-level atom with nondegenerate levels.
We examine theoretically the behavior of cross sections for laser-induced collisional energy transfer (LICET) over a wide range of detunings and laser intensities for the two-atom pairs Li-Sr and Eu-Sr which have been previously studied experimentally. These two cases are complementary in that the laser and collisional interactions enter in opposite orders, and their level structures are such as to give weak-field line shapes of opposite asymmetry and intensity shift. A three-state model is used and the Bambini-Berman formula for the weak-field quasistatic wing is verified. At high intensities the peak cross section is found to go through a maximum and the LICET profile is found to become symmetric about a shifted center with notable departures from a uniform falloff in the far quasistatic wing, apparently arising from radiative collisional interference effects.