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

International Conference on Ultrafast Phenomena

Stimulated photon echo for elastic and depolarizing collision studies

J. Keller, J.-L. Le Gouët

Published Jan 1, 1984• 1 citation
Publisher

Abstract

Among various photon echo phenomena which have been predicted and observed in vapours [1], stimulated photon echo (three pulse echo) is a very attractive tool to investigate angular dependence of collisional processes. Already applied to the study of small angle elastic scattering [2] this method may also prove adequate for studying quasi-resonant inelastic processes involving excited species such as depolarizing collisions, collisional transitions between hyperfine, fine or rotational sublevels, energy pooling collisions. For all these processes total cross sections have already been obtained in the past by different experimental ways. However they deserve to be reexamined in the perspective of their angular dependence.

DOI
10.1364/up.1984.tue17

Related papers

Stimulated photon echo for angular analysis of elastic and depolarizing Yb/emph>– noble-gas collisions

J. Keller, J.-L. Le Gouët

Elastic and depolarizing collisions between excited ytterbium atoms (6s6p ${}^{3}$${P}_{1}$ level) and noble gases (He, Ne, and Xe) are investigated using a stimulated-photon-echo technique. The method is sensitive to collisional velocity changes concerning both the total population ${\ensuremath{\rho}}^{0}$ and the alignment ${\ensuremath{\rho}}^{2}$ of the level. More specifically, it enables us to compare precisely the velocity changes associated with elastic scattering and with alignment-preserving scattering. This represents an improvement with regard to previous works. A detailed theoretical discussion of depolarizing collisions in laser spectroscopy is presented. A simplified density-matrix equation is derived under appropriate approximations. Stimulated photon-echo data for elastic scattering are interpreted within the limits of small-angle scattering in a long-range van der Waals potential; total elastic scattering cross sections are derived from comparison between experiment and calculation: ${\mathit{\ensuremath{\sigma}}}_{\mathrm{He}}^{\mathrm{el}}$=220(20) A${\r{}}^{2}$, ${\mathit{\ensuremath{\sigma}}}_{\mathrm{Ne}}^{\mathrm{el}}$=320(20) A${\r{}}^{2}$, ${\mathit{\ensuremath{\sigma}}}_{\mathrm{Xe}}^{\mathrm{el}}$=1240(60) A${\r{}}^{2}$. Total rates for destruction of alignment are measured in an auxiliary standard photon-echo experiment; the corresponding cross sections are ${\mathit{\ensuremath{\sigma}}}_{\mathrm{He}}^{(2)}$=94(3) A${\r{}}^{2}$, ${\mathit{\ensuremath{\sigma}}}_{\mathrm{Ne}}^{(2)}$=123(7) A${\r{}}^{2}$, ${\mathit{\ensuremath{\sigma}}}_{\mathrm{Xe}}^{(2)}$=300(20) A${\r{}}^{2}$. Stimulated photon-echo data for depolarizing collisions are successfully compared with a calculation that we develop starting from a long-range anisotropic model potential.

Physical Review A•Sep 1, 1985•22 citations

Collision-induced stimulated photon echo at the transition 0–1

Решетов Владимир Александрович, Е. Н. Попов

The stimulated photon echo formed by the sequence of three laser excitation pulses in gaseous medium on the transition with the angular momentum change 0-1 is considered with an account of elastic depolarizing collisions. The polarization properties of this echo may be potentially interesting for the purposes of data processing. It is shown, that with the polarization of the first pulse orthogonal to that of the second and third pulses the appearance of the echo signal will be entirely determined by the action of collisions. The existence of this echo is determined by the difference in the alignment and the orientation relaxation rates of the excited level.

arXiv:1205.5381•Journal of Physics B Atomic Molecular and Optical Physics•Oct 24, 2012•5 citations

Stimulated Photon Echo for Collisional Study in Yb Vapor

J. Keller, J.-L. Le Gouët

With a three-level configuration in ytterbium vapor, we have performed the first quantitative investigation of single excited-level scattering using a stimulated photon echo (three-pulse echo). We have studied the collisional relaxation of the echo signal by rare-gas perturbers and have derived a theoretical expression for the relaxation rate. Total elastic cross sections for collisions between $\mathrm{Yb}(6s6p^{3}P_{1}$) and Ne or Xe have been obtained.

Physical Review Letters•Jun 4, 1984•32 citations

Investigation of elastic and depolarizing collisions in strontium using broadband stimulated photon echoes

M. Saïdi, J. Keller, J.-L. Le Gouët

Elastic and depolarizing collisions between excited strontium (5s 5p 3P1) and noble gases are investigated in a broadband stimulated photon echo (SPE) experiment. The stimulated photon echo signal produced under broadband (incoherent) excitation is calculated in the weak field regime both for correlated and for uncorrelated pulses using a simple statistical model for the light field. The relaxation of the echo signal due to elastic collisions is considered and the complete development of the corresponding propagator is derived. The collisional velocity changes concerning the total population and the alignment are compared precisely in the SPE experiment and the corresponding relaxation rates are measured. A simple long-range Van der Waals potential accounts for population scattering data ; total elastic scattering cross sections are deduced from the comparison of experiment and calculation (σelAr = 583(27) Å2; σ elHe = 190(6) Å2). The collisional model is extended for light perturbers to include both the small angle classical scattering region and the diffractive scattering region. Total rates for destruction of alignment are measured in an auxiliary photon echo experiment (σ (2)He = 91 (4) Å2; ; σ(2) Ne = 102 (14) A2 ; σ(2)Ar = 267 (13 ) Å2 ; σ(2)Kr = 329 (21) Å2 ; σ(2)Xc = 370 (13) Å2). SPE data for depolarization are compared with a calculation based upon a long-range anisotropic model potential.

Journal de physique•Jan 1, 1988•7 citations

Photon echo and stimulated photon echo study of various collisional-relaxation channels

Н. Н. Рубцова, L. S. Vasilenko, Хворостов Евгений Борисович

Collisional relaxation in SF6 gas and its mixtures with He and Xe is studied by photon echo and stimulated photon echo methods from the standpoint of the possibility of identifying the contributions of different types of collisions. The nonexponential nature of the kinetic curve of the photon echo is clearly observed for pure SF6, it is weaker in the mixture SF6+Xe, and it is virtually completely absent for high degrees of dilution of SF6 with helium. These features can be explained on the basis of estimates, made from experimental data, of the critical delay between the exciting pulses (for which the nonexponential behavior should be most strongly manifested). In pure SF6 it is possible to distinguish the contribution of the inelastic channel (rotational relaxation) and the contribution of weak collisions. To distinguish successfully the relaxation channels in mixtures with buffer gases a heavier buffer gas and a much better time resolution must be used. It is shown that data obtained on the orientation and alignment relaxation rates by the stimulated photon echo method can serve as an upper limit for the rates of inelastic processes which cannot be measured by the photon echo method. The combined use of photon echo and stimulated photon echo methods made it possible to obtain data on the cross sections for elastic and inelastic scattering of the collisional pairs SF6–SF6, SF6–Xe, and SF6–He.

Journal of Experimental and Theoretical Physics•Jul 1, 1999•1 citation

The modified stimulated photon echo as a new method for measuring population, orientation and alignment relaxation times

Igor V. Yevseyev, Valery M. Yermachenko, Решетов Владимир Александрович

The modified stimulated photon echo is proposed as a method for the investigation of elastic collisions of excited atoms with non-excited foreign gas atoms, which induce the redistribution of the excited atoms in Zeeman sublevels. Such collisions cause the difference in the population, orientation and alignment relaxation times of a resonant level. It is shown that the proper choice of mutual orientation of the exciting-light polarisation vectors makes it possible to determine the relaxation times for the population, orientation and alignment of a resonant level. It is found that the formulae, derived in the limit of exciting-pulse small areas, are the most attractive for spectroscopic purposes, as in this case the polarisation properties of the modified stimulated photon echo do not depend on the exciting-pulse shapes, nor on their areas. A detailed discussion of the experimental results of Hartmann and collaborators (1979) and of Keller and Le Gouet (1984), mainly concerned with the investigation of the modified stimulated photon echoes in gases, is carried out.

Journal of Physics B Atomic and Molecular Physics•Jan 28, 1986•7 citations
Among various photon echo phenomena which have been predicted and observed in vapours [1], stimulated photon echo (three pulse echo) is a very attractive tool to investigate angular dependence of collisional processes. Already applied to the study of small angle elastic scattering [2] this method may also prove adequate for studying quasi-resonant inelastic processes involving excited species such as depolarizing collisions, collisional transitions between hyperfine, fine or rotational sublevels, energy pooling collisions. For all these processes total cross sections have already been obtained in the past by different experimental ways. However they deserve to be reexamined in the perspective of their angular dependence.
Elastic and depolarizing collisions between excited ytterbium atoms (6s6p 3{}^{3}3P1{P}_{1}P1​ level) and noble gases (He, Ne, and Xe) are investigated using a stimulated-photon-echo technique. The method is sensitive to collisional velocity changes concerning both the total population ${\ensuremath{\rho}}^{0}$ and the alignment ${\ensuremath{\rho}}^{2}$ of the level. More specifically, it enables us to compare precisely the velocity changes associated with elastic scattering and with alignment-preserving scattering. This represents an improvement with regard to previous works. A detailed theoretical discussion of depolarizing collisions in laser spectroscopy is presented. A simplified density-matrix equation is derived under appropriate approximations. Stimulated photon-echo data for elastic scattering are interpreted within the limits of small-angle scattering in a long-range van der Waals potential; total elastic scattering cross sections are derived from comparison between experiment and calculation: ${\mathit{\ensuremath{\sigma}}}_{\mathrm{He}}^{\mathrm{el}}$=220(20) A˚2{\r{}}^{2}˚2, ${\mathit{\ensuremath{\sigma}}}_{\mathrm{Ne}}^{\mathrm{el}}$=320(20) A˚2{\r{}}^{2}˚2, ${\mathit{\ensuremath{\sigma}}}_{\mathrm{Xe}}^{\mathrm{el}}$=1240(60) A˚2{\r{}}^{2}˚2. Total rates for destruction of alignment are measured in an auxiliary standard photon-echo experiment; the corresponding cross sections are ${\mathit{\ensuremath{\sigma}}}_{\mathrm{He}}^{(2)}$=94(3) A˚2{\r{}}^{2}˚2, ${\mathit{\ensuremath{\sigma}}}_{\mathrm{Ne}}^{(2)}$=123(7) A˚2{\r{}}^{2}˚2, ${\mathit{\ensuremath{\sigma}}}_{\mathrm{Xe}}^{(2)}$=300(20) A˚2{\r{}}^{2}˚2. Stimulated photon-echo data for depolarizing collisions are successfully compared with a calculation that we develop starting from a long-range anisotropic model potential.
The stimulated photon echo formed by the sequence of three laser excitation pulses in gaseous medium on the transition with the angular momentum change 0-1 is considered with an account of elastic depolarizing collisions. The polarization properties of this echo may be potentially interesting for the purposes of data processing. It is shown, that with the polarization of the first pulse orthogonal to that of the second and third pulses the appearance of the echo signal will be entirely determined by the action of collisions. The existence of this echo is determined by the difference in the alignment and the orientation relaxation rates of the excited level.
With a three-level configuration in ytterbium vapor, we have performed the first quantitative investigation of single excited-level scattering using a stimulated photon echo (three-pulse echo). We have studied the collisional relaxation of the echo signal by rare-gas perturbers and have derived a theoretical expression for the relaxation rate. Total elastic cross sections for collisions between Yb(6s6p3P1\mathrm{Yb}(6s6p^{3}P_{1}Yb(6s6p3P1​) and Ne or Xe have been obtained.
Elastic and depolarizing collisions between excited strontium (5s 5p 3P1) and noble gases are investigated in a broadband stimulated photon echo (SPE) experiment. The stimulated photon echo signal produced under broadband (incoherent) excitation is calculated in the weak field regime both for correlated and for uncorrelated pulses using a simple statistical model for the light field. The relaxation of the echo signal due to elastic collisions is considered and the complete development of the corresponding propagator is derived. The collisional velocity changes concerning the total population and the alignment are compared precisely in the SPE experiment and the corresponding relaxation rates are measured. A simple long-range Van der Waals potential accounts for population scattering data ; total elastic scattering cross sections are deduced from the comparison of experiment and calculation (σelAr = 583(27) Å2; σ elHe = 190(6) Å2). The collisional model is extended for light perturbers to include both the small angle classical scattering region and the diffractive scattering region. Total rates for destruction of alignment are measured in an auxiliary photon echo experiment (σ (2)He = 91 (4) Å2; ; σ(2) Ne = 102 (14) A2 ; σ(2)Ar = 267 (13 ) Å2 ; σ(2)Kr = 329 (21) Å2 ; σ(2)Xc = 370 (13) Å2). SPE data for depolarization are compared with a calculation based upon a long-range anisotropic model potential.
Collisional relaxation in SF6 gas and its mixtures with He and Xe is studied by photon echo and stimulated photon echo methods from the standpoint of the possibility of identifying the contributions of different types of collisions. The nonexponential nature of the kinetic curve of the photon echo is clearly observed for pure SF6, it is weaker in the mixture SF6+Xe, and it is virtually completely absent for high degrees of dilution of SF6 with helium. These features can be explained on the basis of estimates, made from experimental data, of the critical delay between the exciting pulses (for which the nonexponential behavior should be most strongly manifested). In pure SF6 it is possible to distinguish the contribution of the inelastic channel (rotational relaxation) and the contribution of weak collisions. To distinguish successfully the relaxation channels in mixtures with buffer gases a heavier buffer gas and a much better time resolution must be used. It is shown that data obtained on the orientation and alignment relaxation rates by the stimulated photon echo method can serve as an upper limit for the rates of inelastic processes which cannot be measured by the photon echo method. The combined use of photon echo and stimulated photon echo methods made it possible to obtain data on the cross sections for elastic and inelastic scattering of the collisional pairs SF6–SF6, SF6–Xe, and SF6–He.
The modified stimulated photon echo is proposed as a method for the investigation of elastic collisions of excited atoms with non-excited foreign gas atoms, which induce the redistribution of the excited atoms in Zeeman sublevels. Such collisions cause the difference in the population, orientation and alignment relaxation times of a resonant level. It is shown that the proper choice of mutual orientation of the exciting-light polarisation vectors makes it possible to determine the relaxation times for the population, orientation and alignment of a resonant level. It is found that the formulae, derived in the limit of exciting-pulse small areas, are the most attractive for spectroscopic purposes, as in this case the polarisation properties of the modified stimulated photon echo do not depend on the exciting-pulse shapes, nor on their areas. A detailed discussion of the experimental results of Hartmann and collaborators (1979) and of Keller and Le Gouet (1984), mainly concerned with the investigation of the modified stimulated photon echoes in gases, is carried out.