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

Collisionally induced coherent signals and collisional redistribution

M. Dagenais

Published Aug 1, 1982• 23 citations
Publisher

Abstract

It is demonstrated that, in the presence of collisions and for nonresonant lasers, it is energetically possible to access resonantly excited states and induce a coherence between the states. This situation cannot arise in the absence of collisions if the starting state does not decay. This explains why, when collisions are introduced, a new signal can be generated in a wave-mixing type of experiment. The collisionally induced generation of a coherent signal is intimately related to the process of collisional redistribution. It is shown that all the collisionally induced coherent signals that have been reported up to now involve putting real populations in the excited states. This fact has not always been fully appreciated. No resonance between unpopulated states can exist. The time dependence of these new coherent signals is briefly discussed. In the case of a Raman resonance between equally populated states, it is pointed out that new coherent pathways of equal importance should be considered for explaining the experimental results. A new pressure-induced signal in four-wave mixing is also discussed. It is called "collisionally triggered two-photon quasiresonant coherent signal."

DOI
10.1103/physreva.26.869

Related papers

Collisionally triggered generation of a coherent signal

M. Dagenais

We demonstrate the generation of a coherent signal by an incoherent process. In a first step, population is transferred from the ground state to two excited states by a collisional redistribution process. Then, in a second step, a coherent Raman signal is generated from these two populated excited states. At high pressure, it is predicted that a Raman-type resonance between two equally populated levels should be observed. Information about inelastic-collision cross sections and dephasing coefficients in the excited states is obtained.

Physical Review A•Sep 1, 1981•18 citations

Theoretical study of atom collision by two-nondegenerate four-wave mixing

孙江 Sun Jiang, Xiaoyang Chang, Su-Heng Zhang +1 more

In recent years, the collisional redistribution of radiation and collision-induced broadening of Rydberg atomic spectral lines by buffer gas perturbation have aroused the renewed interest. Rydberg atoms having a large dipole moment and long lifetime can interact with each other coherently for relatively long time, which makes them a potential candidate for quantum information processing. Besides, collisional redistribution has an important potential application in laser cooling and trapping. Based on previous experimental data, in this paper, two-nondegenerate four-wave mixing (NFWM) for studying atom collision, composed of two-photon resonant NFWM and collisional redistribution NFWM, is reported. The spectrum variation of the two-NFWM affected by the pressure, temperature, detuning and collision-broadening rate coefficient is analyzed. The principle of two-NFWM involving three incident beams is explained as follows. Consider two-NFWM in a |0-|1-|2 cascade three-level system, where states between |0 and |1 and between |1 and |2 ightangle are coupled by resonant frequencies 1 and 2 , respectively. Beam 1 with frequency 1 propagates along the direction opposite to the direction of beam 2, beams 2 and 2' have the same frequency 2, and between their directions there exists a small angle. Assuming that 1 1 and 2 2 so that 1 drives the transition from |0 to |1 while 2 drives the transition from |1 to |2, the simultaneous interactions of atoms with beams 1 and 2 will induce atomic coherence between |0 and |2 through two-photon excitation. This coherence is probed by beam 2', and as a result a two-photon resonant NFWM signal of frequency 1 is generated in the direction almost opposite to the direction of beam 2'. To avoid strong absorption at the resonant frequency of transition from |0 to |1, here the wavelength of beam1 is detuned from the exact resonance. An atom population of level |1 caused by collisional redistribution can be induced when a certain buffer gas pressure is imposed. The collisional redistribution NFWM process also exists in this case. Beam 2 drives the transition from |1 to |2 to induce an atomic coherence which is probed by beam 2' for giving rise to an atomic population grating. A collisional redistribution NFWM signal propagating along the same direction as the two-photon resonant NFWM signal is generated when beam 1 is scattered by the grating. Much information about atomic collisions can be obtained by analyzing the two NFWM signals. In a cascade three-level system composed of ground state, intermediate state and Rydberg state, and the two-NFWM can be used to investigate not only the broadening and shifting of the Rydberg level but also the collisional redistribution of the intermediate state. Unlike other experiments studying the pressure dependence of the longitudinal relaxation rate of atom states, this technique is a purely optical coherent means, and can measure the transverse relaxation rate 20 between Rydberg state and ground state as well as the pressure dependence of the transverse relaxation rate 21 between Rydberg state and intermediate state.

Acta Physica Sinica•Jan 1, 2016•0 citations

Theory of electronic-state coherences produced in combined laser-field—collisional reactions

P. R. Berman, E. Giacobino

A method for producing electronic-state coherences using either collisionally-aided radiative excitation (or "optical collision") or laser-induced collisional energy transfer (or "radiative collision") is proposed. Two atoms, $A$ and ${A}^{\ensuremath{'}}$, collide in the presence of two pulsed-laser fields having frequencies $\ensuremath{\Omega}$ and ${\ensuremath{\Omega}}_{1}$. It is shown that by choosing ${\ensuremath{\Omega}}_{1}\ifmmode\pm\else\textpm\fi{}\ensuremath{\Omega}$ such that an energy-conserving transition can occur in the composite $A{A}^{\ensuremath{'}}$ system, one can create an electronic-state coherence in the $A$ or ${A}^{\ensuremath{'}}$ atoms. The coherence can be produced between states of the same or of opposite parity; if it is between states of opposite parity, coherent emission at frequency ${\ensuremath{\Omega}}_{1}\ifmmode\pm\else\textpm\fi{}\ensuremath{\Omega}$ may be generated. The relationship of this work to theories of "pressure-induced extra resonances" in four-wave mixing is discussed.

Physical Review A•Nov 1, 1983•13 citations

Frequency non-mutuality of collision-induced four-wave mixing signal

S. Ya. Kilin, A F Fedorov

It is shown that the collision-induced four-wave mixing signal in two-photon quasi-resonant excitation has the property of frequency non-mutuality, i.e. when the probe field frequency omega s is replaced by the signal frequency omega out the four-wave mixing coherent signal does not arise. The reason for such frequency non-mutuality lies in the nature of the collision-induced coherent scattering. It is shown that this scattering occurs because of double non-adiabatic transitions (as affected by collisions) between the states of a dressed atom without changing the environment (buffer) state during the four-photon-scattering elementary process; this scattering will be referred to as coherent collisionally double induced scattering (CCDIS).

Journal of Physics B Atomic and Molecular Physics•Sep 14, 1986•2 citations

Pressure-Induced Extra Resonances in Four-Wave Mixing

Yehiam Prior, A. R. Bogdan, M. Dagenais +1 more

The first observation of pressure-induced extra resonant enhancements of a coherent four-wave---mixing signal is reported. When the difference between two input frequencies, ${\ensuremath{\omega}}_{1}$ and ${\ensuremath{\omega}}_{2}$, corresponds to the separation of two unpopulated upper levels, a resonant enhancement of the generated intensity at $2{\ensuremath{\omega}}_{1}\ensuremath{-}{\ensuremath{\omega}}_{2}$ is caused by collisions.

Physical Review Letters•Jan 12, 1981•249 citations

Nonimpact theory of four-wave mixing and intracollisional dynamics

Yehiam Prior, A. Ben‐Reuven

A unified theory of coherent and incoherent resonance scattering of radiation in gases is presented. Expressions for the scattering rates in collisional redistribution and four-wave mixing (FWM) are obtained, starting from a microscopic formulation based on the Liouville--von Neumann equation. The derivation reemphasizes the point that coherent scattering depends on a product of scattering amplitudes at two separate points in the gas. The theory is extended to the nonimpact domain in which frequency detunings exceed the inverse duration of a single collision, taking into account intracollisional effects. Expressions are given in the so-called quasistatic limit (of semiclassical Franck-Condon transitions) for situations in which one or more radiative transitions occur during the collision. An extension of double-sided diagrams to collision-induced processes is introduced, and is used to illustrate the various phenomena described. Applications are suggested to the study of molecular dynamics, making use of the spectral features of FWM outside the impact domain. Investigations of long-range correlation effects, involving laser fluctuations, or cooperative excitations in dense fluids (utilizing the two-point nature of FWM), are also discussed.

Physical Review A•Apr 1, 1986•15 citations
It is demonstrated that, in the presence of collisions and for nonresonant lasers, it is energetically possible to access resonantly excited states and induce a coherence between the states. This situation cannot arise in the absence of collisions if the starting state does not decay. This explains why, when collisions are introduced, a new signal can be generated in a wave-mixing type of experiment. The collisionally induced generation of a coherent signal is intimately related to the process of collisional redistribution. It is shown that all the collisionally induced coherent signals that have been reported up to now involve putting real populations in the excited states. This fact has not always been fully appreciated. No resonance between unpopulated states can exist. The time dependence of these new coherent signals is briefly discussed. In the case of a Raman resonance between equally populated states, it is pointed out that new coherent pathways of equal importance should be considered for explaining the experimental results. A new pressure-induced signal in four-wave mixing is also discussed. It is called "collisionally triggered two-photon quasiresonant coherent signal."
We demonstrate the generation of a coherent signal by an incoherent process. In a first step, population is transferred from the ground state to two excited states by a collisional redistribution process. Then, in a second step, a coherent Raman signal is generated from these two populated excited states. At high pressure, it is predicted that a Raman-type resonance between two equally populated levels should be observed. Information about inelastic-collision cross sections and dephasing coefficients in the excited states is obtained.
In recent years, the collisional redistribution of radiation and collision-induced broadening of Rydberg atomic spectral lines by buffer gas perturbation have aroused the renewed interest. Rydberg atoms having a large dipole moment and long lifetime can interact with each other coherently for relatively long time, which makes them a potential candidate for quantum information processing. Besides, collisional redistribution has an important potential application in laser cooling and trapping. Based on previous experimental data, in this paper, two-nondegenerate four-wave mixing (NFWM) for studying atom collision, composed of two-photon resonant NFWM and collisional redistribution NFWM, is reported. The spectrum variation of the two-NFWM affected by the pressure, temperature, detuning and collision-broadening rate coefficient is analyzed. The principle of two-NFWM involving three incident beams is explained as follows. Consider two-NFWM in a |0-|1-|2 cascade three-level system, where states between |0 and |1 and between |1 and |2 ightangle are coupled by resonant frequencies 1 and 2 , respectively. Beam 1 with frequency 1 propagates along the direction opposite to the direction of beam 2, beams 2 and 2' have the same frequency 2, and between their directions there exists a small angle. Assuming that 1 1 and 2 2 so that 1 drives the transition from |0 to |1 while 2 drives the transition from |1 to |2, the simultaneous interactions of atoms with beams 1 and 2 will induce atomic coherence between |0 and |2 through two-photon excitation. This coherence is probed by beam 2', and as a result a two-photon resonant NFWM signal of frequency 1 is generated in the direction almost opposite to the direction of beam 2'. To avoid strong absorption at the resonant frequency of transition from |0 to |1, here the wavelength of beam1 is detuned from the exact resonance. An atom population of level |1 caused by collisional redistribution can be induced when a certain buffer gas pressure is imposed. The collisional redistribution NFWM process also exists in this case. Beam 2 drives the transition from |1 to |2 to induce an atomic coherence which is probed by beam 2' for giving rise to an atomic population grating. A collisional redistribution NFWM signal propagating along the same direction as the two-photon resonant NFWM signal is generated when beam 1 is scattered by the grating. Much information about atomic collisions can be obtained by analyzing the two NFWM signals. In a cascade three-level system composed of ground state, intermediate state and Rydberg state, and the two-NFWM can be used to investigate not only the broadening and shifting of the Rydberg level but also the collisional redistribution of the intermediate state. Unlike other experiments studying the pressure dependence of the longitudinal relaxation rate of atom states, this technique is a purely optical coherent means, and can measure the transverse relaxation rate 20 between Rydberg state and ground state as well as the pressure dependence of the transverse relaxation rate 21 between Rydberg state and intermediate state.
A method for producing electronic-state coherences using either collisionally-aided radiative excitation (or "optical collision") or laser-induced collisional energy transfer (or "radiative collision") is proposed. Two atoms, AAA and ${A}^{\ensuremath{'}}$, collide in the presence of two pulsed-laser fields having frequencies $\ensuremath{\Omega}$ and ${\ensuremath{\Omega}}_{1}$. It is shown that by choosing ${\ensuremath{\Omega}}_{1}\ifmmode\pm\else\textpm\fi{}\ensuremath{\Omega}$ such that an energy-conserving transition can occur in the composite $A{A}^{\ensuremath{'}}$ system, one can create an electronic-state coherence in the AAA or ${A}^{\ensuremath{'}}$ atoms. The coherence can be produced between states of the same or of opposite parity; if it is between states of opposite parity, coherent emission at frequency ${\ensuremath{\Omega}}_{1}\ifmmode\pm\else\textpm\fi{}\ensuremath{\Omega}$ may be generated. The relationship of this work to theories of "pressure-induced extra resonances" in four-wave mixing is discussed.
It is shown that the collision-induced four-wave mixing signal in two-photon quasi-resonant excitation has the property of frequency non-mutuality, i.e. when the probe field frequency omega s is replaced by the signal frequency omega out the four-wave mixing coherent signal does not arise. The reason for such frequency non-mutuality lies in the nature of the collision-induced coherent scattering. It is shown that this scattering occurs because of double non-adiabatic transitions (as affected by collisions) between the states of a dressed atom without changing the environment (buffer) state during the four-photon-scattering elementary process; this scattering will be referred to as coherent collisionally double induced scattering (CCDIS).
A unified theory of coherent and incoherent resonance scattering of radiation in gases is presented. Expressions for the scattering rates in collisional redistribution and four-wave mixing (FWM) are obtained, starting from a microscopic formulation based on the Liouville--von Neumann equation. The derivation reemphasizes the point that coherent scattering depends on a product of scattering amplitudes at two separate points in the gas. The theory is extended to the nonimpact domain in which frequency detunings exceed the inverse duration of a single collision, taking into account intracollisional effects. Expressions are given in the so-called quasistatic limit (of semiclassical Franck-Condon transitions) for situations in which one or more radiative transitions occur during the collision. An extension of double-sided diagrams to collision-induced processes is introduced, and is used to illustrate the various phenomena described. Applications are suggested to the study of molecular dynamics, making use of the spectral features of FWM outside the impact domain. Investigations of long-range correlation effects, involving laser fluctuations, or cooperative excitations in dense fluids (utilizing the two-point nature of FWM), are also discussed.