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

Coherent Raman scattering in a low pressure gas

Jacques Moret‐Bailly

Published Jan 26, 2020• 0 citations
OpenAlex

Abstract

Incoherent emissions of light by a gas require collisions of molecules, while coherent emissions, at low pressure, are amplifications of pre-existing rays. At very low pressure, very accidental collisions of atoms of an excited gas initiate flare-ups, and Raman pumping of the gas by a temporally incoherent ray of light absorbs molecular quanta without other energy diffusion.

Related papers

A Study of the Macroscopic Quantum Fluctuations of Stimulated Raman Scattering from a Partially Coherent Source

Michael G. Raymer, Ian A. Walmsley

A pencil shaped region of a Raman-active medium forms a source for Stokes-shifted light via stimulated Raman Scattering (SRS) when driven by an intense laser pulse. Stokes photons are scattered spontaneously at first, and then amplified during propagation through the medium. Since the scattering is initiated by quantum noise, the actual number of photons produced in any given pulse will be highly uncertain, even if the pulse energy of the driving laser is constant1. As the Stokes light propagates through such an extended region, it's coherence properties will be changed. The spatial coherence is determined by the size and shape of the region, which may be characterized by its Fresnel number F, defined as F= A/λSL, where A is the cross-sectional area of the interaction region, which has length L, and λS is the Stokes wavelength. The rate at which the microscopic scatterers (atoms or molecules) are dephased by collisions affects the temporal coherence of the Stokes light, characterised by the temporal coherence parameter Γτ /gL, where Γ is the collisional dephasing rate, τ is the laser pulse duration and g is the steady-state Raman gain coefficient.

International Meeting on Instabilities and Dynamics of Lasers and Nonlinear Optical Systems•Jan 1, 1985•0 citations

White light through low pressure H atoms.

Jacques Moret‐Bailly

Propagation of white light in very low pressure, relatively cold H atoms of space, is spatially coherent. Lyman alpha absorption pumps atoms to 2P states. Stimulated Raman losses (SRL) using fine levels quanta of excited H, redshift light at all frequencies until an alpha superradiant flare de-excites H and super-absorbs a black line of a Lyman forest. Pumping stops when an absorbed line is shifted to alpha frequency, so that beta and gamma lines are visibly absorbed. If there is energy enough at Lyman beta frequency, a similar, slow redshift restarts the process. A quasar H spectrum is generated. Hubble redshift evaluates a column density of H in 2P state.

•Jul 15, 2019•0 citations

Raman scattering in an atomic gas in the presence of depolarizing collisions

A. I. Alekseev

Journal of Experimental and Theoretical Physics•Mar 1, 1990•0 citations

Saturation spectroscopy of coherent raman scattering in molecular gases

Victor N. Zadkov, Nikolai I Koroteev, M. V. Rychov +1 more

Applied Physics B•Jul 1, 1984•9 citations

Coherence and control in photo-molecular wave packet dynamics

Alex C. Han

Wave-mechanical phenomena such as resonance and interference, in both light and matter, are central to the principles of quantum coherent control over molecular processes. Focusing on the dynamical aspects, this dissertation is a compilation of studies on the interaction physics involving wave packets in molecules, the driving light field, and the underlying coherence and control. In each work, we will demonstrate interesting correlations between the properties of a carefully designed excitation light field and desirable outcomes of the molecules quantum dynamics. We will analyze the dynamical effect of a Feshbach resonance in the adiabatic Raman photoassociation for ultracold diatomic molecule formation from ultracold atoms. A narrow resonance is shown to be able to increase the effective number of collisions, in an ultracold atomic gas, that are available for photoassociation. This results in an optimal resonance width much smaller than the atomic collision energy bandwidth, due to the balance between the effective collision rate and single-collision transfer probability. Next, we demonstrate the linear molecular response to high-intensity, broadband, shaped optical fields. We show that this originates from interferences based on intra-pulse Raman excitations, and thus response linearity is not unique to the first-order perturbative limit and can not be used to infer the strength of the field. In the last study, we simulate the stochastic vibrational wave packet and dissociation-flux dynamics in a molecule excited by light with temporal and spectral incoherent properties. Between this case and that using a coherent pulse with the same spectral profile, we compare the vibrational wave functions and the loss of electronic and vibrational coherence, and demonstrate the qualitative difference between coherently and incoherently driven dynamics in molecules.

•Jan 1, 2015•0 citations

Green Function Theory of Resonance Light-Pulse Scattering. I: Simple Application to Molecular Spectroscopy

Masami Kusunoki

A thermal Green function theory of resonance long-laser-pulse scattering is developed, correctly taking account of the uncertainty-relation between the time-resolved and the energy-resolved experiments and the effect of the sample surface. The transient scattering efficiency can be calculated by folding the retarded Green's functions which are given by the thermal average of the chronological products of the pulse-current (or -density) and current operators into an uncertainty-principle broadening function. The theory is applied to resonance light scattering from a simple molecule in gas for steady and transient cases, where all the collision processes are treated quantum-statistically. At low pressure, the resonance scattering is mainly composed of Raman scattering (RS), final-state redistribution scattering (FRS), final-state transfer scattering (FTS) and collision-induced redistribution scattering (CIRS). In the steady state, it is shown that ordinary resonance Raman scattering is equivalent to RS in collisionless case, that absorption followed by emission contains RS, FRS and FTS, and that absorption followed by redistribution followed by emission is the same phenomenon as CIRS which is weighted by rotational population of excited molecules. Moreover, recent laser-pulse data by Roussea, Patterson and Williams are satisfactorily explained. Connection between this theory and other work is discussed.

Progress of Theoretical Physics•Mar 1, 1976•6 citations
Incoherent emissions of light by a gas require collisions of molecules, while coherent emissions, at low pressure, are amplifications of pre-existing rays. At very low pressure, very accidental collisions of atoms of an excited gas initiate flare-ups, and Raman pumping of the gas by a temporally incoherent ray of light absorbs molecular quanta without other energy diffusion.
A pencil shaped region of a Raman-active medium forms a source for Stokes-shifted light via stimulated Raman Scattering (SRS) when driven by an intense laser pulse. Stokes photons are scattered spontaneously at first, and then amplified during propagation through the medium. Since the scattering is initiated by quantum noise, the actual number of photons produced in any given pulse will be highly uncertain, even if the pulse energy of the driving laser is constant1. As the Stokes light propagates through such an extended region, it's coherence properties will be changed. The spatial coherence is determined by the size and shape of the region, which may be characterized by its Fresnel number F, defined as F= A/λSL, where A is the cross-sectional area of the interaction region, which has length L, and λS is the Stokes wavelength. The rate at which the microscopic scatterers (atoms or molecules) are dephased by collisions affects the temporal coherence of the Stokes light, characterised by the temporal coherence parameter Γτ /gL, where Γ is the collisional dephasing rate, τ is the laser pulse duration and g is the steady-state Raman gain coefficient.
Propagation of white light in very low pressure, relatively cold H atoms of space, is spatially coherent. Lyman alpha absorption pumps atoms to 2P states. Stimulated Raman losses (SRL) using fine levels quanta of excited H, redshift light at all frequencies until an alpha superradiant flare de-excites H and super-absorbs a black line of a Lyman forest. Pumping stops when an absorbed line is shifted to alpha frequency, so that beta and gamma lines are visibly absorbed. If there is energy enough at Lyman beta frequency, a similar, slow redshift restarts the process. A quasar H spectrum is generated. Hubble redshift evaluates a column density of H in 2P state.
Wave-mechanical phenomena such as resonance and interference, in both light and matter, are central to the principles of quantum coherent control over molecular processes. Focusing on the dynamical aspects, this dissertation is a compilation of studies on the interaction physics involving wave packets in molecules, the driving light field, and the underlying coherence and control. In each work, we will demonstrate interesting correlations between the properties of a carefully designed excitation light field and desirable outcomes of the molecules quantum dynamics. We will analyze the dynamical effect of a Feshbach resonance in the adiabatic Raman photoassociation for ultracold diatomic molecule formation from ultracold atoms. A narrow resonance is shown to be able to increase the effective number of collisions, in an ultracold atomic gas, that are available for photoassociation. This results in an optimal resonance width much smaller than the atomic collision energy bandwidth, due to the balance between the effective collision rate and single-collision transfer probability. Next, we demonstrate the linear molecular response to high-intensity, broadband, shaped optical fields. We show that this originates from interferences based on intra-pulse Raman excitations, and thus response linearity is not unique to the first-order perturbative limit and can not be used to infer the strength of the field. In the last study, we simulate the stochastic vibrational wave packet and dissociation-flux dynamics in a molecule excited by light with temporal and spectral incoherent properties. Between this case and that using a coherent pulse with the same spectral profile, we compare the vibrational wave functions and the loss of electronic and vibrational coherence, and demonstrate the qualitative difference between coherently and incoherently driven dynamics in molecules.
A thermal Green function theory of resonance long-laser-pulse scattering is developed, correctly taking account of the uncertainty-relation between the time-resolved and the energy-resolved experiments and the effect of the sample surface. The transient scattering efficiency can be calculated by folding the retarded Green's functions which are given by the thermal average of the chronological products of the pulse-current (or -density) and current operators into an uncertainty-principle broadening function. The theory is applied to resonance light scattering from a simple molecule in gas for steady and transient cases, where all the collision processes are treated quantum-statistically. At low pressure, the resonance scattering is mainly composed of Raman scattering (RS), final-state redistribution scattering (FRS), final-state transfer scattering (FTS) and collision-induced redistribution scattering (CIRS). In the steady state, it is shown that ordinary resonance Raman scattering is equivalent to RS in collisionless case, that absorption followed by emission contains RS, FRS and FTS, and that absorption followed by redistribution followed by emission is the same phenomenon as CIRS which is weighted by rotational population of excited molecules. Moreover, recent laser-pulse data by Roussea, Patterson and Williams are satisfactorily explained. Connection between this theory and other work is discussed.