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

Canadian Journal of Physics

Inelastic collisions and fluorescence in gases

Haider R. Zaidi

Published Sep 1, 1979• 3 citations
Publisher

Abstract

The fluorescence spectrum from a multilevel system, in the presence of inelastic collisions which couple the upper states, is calculated in the impact limit. The results are expressed in terms of the collision rates (elastic and inelastic), the collision broadening rates, and the natural damping rates. The integrated intensities are also calculated, and the results are compared with the rate equation results. It is shown that the standard rate equation analysis of the experimental data is not valid when the lower state interaction is significant. The Doppler effect is also included in the general theory of the fluorescent line shapes, and the modification of the profile because of the velocity dependence of the collision rates is discussed.

DOI
10.1139/p79-214

Related papers

The Effect of Collisions on the Resonance Fluorescence Spectrum of Three-Level Atoms with a V-Configuration of Levels

А. И. Пархоменко, Anatolii M. Shalagin

The effect of collisions on the resonance fluorescence spectrum of three-level atoms with a V-configuration of levels when excited by two monochromatic resonance fields has been theoretically investigated. The analysis has been carried out for the systems with a small Doppler broadening compared to the collision frequency (high buffer gas pressures) and for the general case of an arbitrary change (from complete failure to complete preservation) of the phase memory at any of the three transitions in the V-system. It has been shown that in the three-level V-type atoms excited by two monochromatic fields, the resonant fluorescence spectrum (the number of spectral lines and their widths) at one of the transitions strongly depends on the presence of resonant radiation at the adjacent transition. Under certain conditions, the line widths will be completely determined by the relaxation characteristics of the adjacent transition and, in particular, can be repeatedly narrowed with an increase in the radiation intensity at the adjacent transition. It has been shown that despite the homogeneous nature of the broadening of the absorption lines, the resonance fluorescence spectrum has a pronounced anisotropy with respect to the mutual orientation of the wave vectors of spontaneous and exciting radiation. It has been established that the line widths in the resonance fluorescence spectrum are proportional to the diffusion coefficient of the atoms interacting with radiation under certain conditions. This fact can serve as the basis for a spectroscopic method for measuring the transport frequencies of the collisions of the radiation-absorbing particles with the buffer ones. It has been shown that the effects of phase memory in the collisions lead to a strong qualitative and quantitative modification of the resonance fluorescence spectrum.

Optics and Spectroscopy•Dec 1, 2021•1 citation

Theory of collision effects in Doppler-free spectroscopy

P. R. Berman

A theory of the influence of binary collisions on the line shapes associated with Doppler-free spectroscopy is presented. The specific calculation is for two-photon absorption through a real or virtual intermediate state, but the extension of the results to alternative level schemes is included. Collisions are treated quite generally at first, but, ultimately, a simple but reasonable collision model is adopted to properly account for both the "phase-interrupting" and "velocity-changing" aspects of collisions. It is shown that collisional processes can be used to distinguish between the "two-quantum" and "stepwise" contributions to the two-photon excitation rate. Moreover, it is demonstrated that systematic experimental line-shape investigations, in addition to providing tests of current collision theories, can lead to values for collision broadening and shift parameters, excitation transfer rates, magnetic substate relaxation rates, velocity-changing collision rates, and collision kernels. Consequently, Doppler-free spectroscopy can provide a new and important probe of collision effects in atomic and molecular systems.

Physical Review A•Jun 1, 1976•49 citations

Collisional effects in gas lasers

Ashish Agarwal, Rupamanjari Ghosh

The effects of phase-interrupting and velocity-changing collisions between active and perturber atoms on the spectral profile of a gas laser are studied. Exact analytical results for the density matrix are presented for the case of strong collisions in a unidirectional ring laser, and the laser intensity is then evaluated in the Doppler limit under the condition of self-consistency. The washout of the hole burning in the steady-state population difference and the broadening of the laser line shape are discussed. The results of the third-order perturbation theory are compared with the exact calculations valid for an arbitrarily intense pump.

Physical Review A•Feb 1, 1993•2 citations

Analytic expressions for fluorescence spectra and optical collision rates of collisionally perturbed atoms in a strong driving field

F. Schuller, Gerard Nienhuis

We have studied the problem of a collisionally perturbed two-level atom in an intense driving field by developing a method which allows us to calculate the field-dependent collision operator in terms of the low intensity field-independent line-broadening function arising in the usual unified theory of pressure broadening. Our relations are exact to all orders in the field in the limiting case of weak collisions, but they are exact also in the complementary case of strong collisions and weak fields. We apply our results to derive explicit expressions for the rate of optical collisions, the fluorescence spectrum in the case of well-separated components, and the absorption during an adiabatic square pulse.

Canadian Journal of Physics•Feb 1, 1984•6 citations

Effect of collisions on the resonance fluorescence spectrum

А. И. Пархоменко, Anatolii M. Shalagin

The effect of collisions on the resonance fluorescence spectrum of two-level atoms excited by monochromatic resonance radiation is studied. Analysis is performed for systems where the Doppler broadening is small compared to the collision frequency (high buffer gas pressures) and for the general case where collisions arbitrarily change the phase of the radiation-induced dipole moment (from completely interrupted to completely unaffected phase of the dipole moment). Both at a relatively low and at a high excitation radiation intensity, the resonance fluorescence spectrum is shown to depend on whether the two-level system is closed or open. This is especially true for the narrow unshifted Rayleigh scattering line. It is shown that, although the absorption line is homogeneously broadened, the resonance fluorescence spectrum exhibits a clearly pronounced anisotropy. In a direction close to the direction of propagation of the excitation radiation, the Rayleigh scattering line is maximally narrowed. Under certain conditions (that can easily be created in experiments), the width of this line is proportional to the diffusion coefficient of atoms interacting with the radiation.

Journal of Experimental and Theoretical Physics•May 1, 2008•1 citation

Inelastic collisions of virtually excited atoms

Robert E. Walkup, Alan L. Migdall, David E. Pritchard

We report observations of inelastic collisions of atoms excited by a weak monochromatic laser field whose frequency is close to the resonance frequency of the transition from the ground state to an excited state. Our experiments use sodium atoms in a gas cell with the laser frequency detuning from resonance ($|\ensuremath{\Delta}|<6$ GHz) much smaller than the inverse of a collision duration. In this frequency region, our results may be interpreted in terms of inelastic collisions involving virtually excited atoms. The inelastic collision rate is determined by measuring the ratio of fluorescence from the collisionally populated level to emission from the laser populated level. By studying this emission ratio as a function of perturber pressure we show that the inelastic collision rate constant for virtually excited atoms is the same as the thermally averaged rate constant for level-to-level population transfer. Measurements of the emission ratio as a function of the laser detuning from resonance explicitly show how the correlation of collision rates with excitation frequency due to the Doppler effect is lost as the laser is tuned more than several Doppler widths from line center. The collisions of virtually excited atoms fundamentally limit experiments utilizing the Doppler effect to obtain velocity-dependent excited-state collision rates.

Physical Review A•May 1, 1984•3 citations
The fluorescence spectrum from a multilevel system, in the presence of inelastic collisions which couple the upper states, is calculated in the impact limit. The results are expressed in terms of the collision rates (elastic and inelastic), the collision broadening rates, and the natural damping rates. The integrated intensities are also calculated, and the results are compared with the rate equation results. It is shown that the standard rate equation analysis of the experimental data is not valid when the lower state interaction is significant. The Doppler effect is also included in the general theory of the fluorescent line shapes, and the modification of the profile because of the velocity dependence of the collision rates is discussed.
The effect of collisions on the resonance fluorescence spectrum of three-level atoms with a V-configuration of levels when excited by two monochromatic resonance fields has been theoretically investigated. The analysis has been carried out for the systems with a small Doppler broadening compared to the collision frequency (high buffer gas pressures) and for the general case of an arbitrary change (from complete failure to complete preservation) of the phase memory at any of the three transitions in the V-system. It has been shown that in the three-level V-type atoms excited by two monochromatic fields, the resonant fluorescence spectrum (the number of spectral lines and their widths) at one of the transitions strongly depends on the presence of resonant radiation at the adjacent transition. Under certain conditions, the line widths will be completely determined by the relaxation characteristics of the adjacent transition and, in particular, can be repeatedly narrowed with an increase in the radiation intensity at the adjacent transition. It has been shown that despite the homogeneous nature of the broadening of the absorption lines, the resonance fluorescence spectrum has a pronounced anisotropy with respect to the mutual orientation of the wave vectors of spontaneous and exciting radiation. It has been established that the line widths in the resonance fluorescence spectrum are proportional to the diffusion coefficient of the atoms interacting with radiation under certain conditions. This fact can serve as the basis for a spectroscopic method for measuring the transport frequencies of the collisions of the radiation-absorbing particles with the buffer ones. It has been shown that the effects of phase memory in the collisions lead to a strong qualitative and quantitative modification of the resonance fluorescence spectrum.
A theory of the influence of binary collisions on the line shapes associated with Doppler-free spectroscopy is presented. The specific calculation is for two-photon absorption through a real or virtual intermediate state, but the extension of the results to alternative level schemes is included. Collisions are treated quite generally at first, but, ultimately, a simple but reasonable collision model is adopted to properly account for both the "phase-interrupting" and "velocity-changing" aspects of collisions. It is shown that collisional processes can be used to distinguish between the "two-quantum" and "stepwise" contributions to the two-photon excitation rate. Moreover, it is demonstrated that systematic experimental line-shape investigations, in addition to providing tests of current collision theories, can lead to values for collision broadening and shift parameters, excitation transfer rates, magnetic substate relaxation rates, velocity-changing collision rates, and collision kernels. Consequently, Doppler-free spectroscopy can provide a new and important probe of collision effects in atomic and molecular systems.
The effects of phase-interrupting and velocity-changing collisions between active and perturber atoms on the spectral profile of a gas laser are studied. Exact analytical results for the density matrix are presented for the case of strong collisions in a unidirectional ring laser, and the laser intensity is then evaluated in the Doppler limit under the condition of self-consistency. The washout of the hole burning in the steady-state population difference and the broadening of the laser line shape are discussed. The results of the third-order perturbation theory are compared with the exact calculations valid for an arbitrarily intense pump.
We have studied the problem of a collisionally perturbed two-level atom in an intense driving field by developing a method which allows us to calculate the field-dependent collision operator in terms of the low intensity field-independent line-broadening function arising in the usual unified theory of pressure broadening. Our relations are exact to all orders in the field in the limiting case of weak collisions, but they are exact also in the complementary case of strong collisions and weak fields. We apply our results to derive explicit expressions for the rate of optical collisions, the fluorescence spectrum in the case of well-separated components, and the absorption during an adiabatic square pulse.
The effect of collisions on the resonance fluorescence spectrum of two-level atoms excited by monochromatic resonance radiation is studied. Analysis is performed for systems where the Doppler broadening is small compared to the collision frequency (high buffer gas pressures) and for the general case where collisions arbitrarily change the phase of the radiation-induced dipole moment (from completely interrupted to completely unaffected phase of the dipole moment). Both at a relatively low and at a high excitation radiation intensity, the resonance fluorescence spectrum is shown to depend on whether the two-level system is closed or open. This is especially true for the narrow unshifted Rayleigh scattering line. It is shown that, although the absorption line is homogeneously broadened, the resonance fluorescence spectrum exhibits a clearly pronounced anisotropy. In a direction close to the direction of propagation of the excitation radiation, the Rayleigh scattering line is maximally narrowed. Under certain conditions (that can easily be created in experiments), the width of this line is proportional to the diffusion coefficient of atoms interacting with the radiation.
We report observations of inelastic collisions of atoms excited by a weak monochromatic laser field whose frequency is close to the resonance frequency of the transition from the ground state to an excited state. Our experiments use sodium atoms in a gas cell with the laser frequency detuning from resonance ($|\ensuremath{\Delta}|<6$ GHz) much smaller than the inverse of a collision duration. In this frequency region, our results may be interpreted in terms of inelastic collisions involving virtually excited atoms. The inelastic collision rate is determined by measuring the ratio of fluorescence from the collisionally populated level to emission from the laser populated level. By studying this emission ratio as a function of perturber pressure we show that the inelastic collision rate constant for virtually excited atoms is the same as the thermally averaged rate constant for level-to-level population transfer. Measurements of the emission ratio as a function of the laser detuning from resonance explicitly show how the correlation of collision rates with excitation frequency due to the Doppler effect is lost as the laser is tuned more than several Doppler widths from line center. The collisions of virtually excited atoms fundamentally limit experiments utilizing the Doppler effect to obtain velocity-dependent excited-state collision rates.