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.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 ASep 1, 198522 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.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 physiqueJan 1, 19887 citations

Stimulated photon echo for elastic and depolarizing collision studies

J. Keller, J.-L. Le Gouët

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.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.

International Conference on Ultrafast PhenomenaJan 1, 19841 citation

Collision-induced stimulated photon echo

I. V. Evseev, Решетов Владимир Александрович

OptSpAug 1, 19880 citations

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.