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

Problems associated with the measurement of coherence parameters: Superelastic electron scattering by laser-excited Ba138 (...6s6p P11 ) atoms

P W Zetner, Sandor Trajmar, George Csanak, Robert E. H. Clark

Published Jun 1, 1989• 22 citations
Publisher

Abstract

Measurements of superelastic scattering of electrons by laser-excited $^{138}\mathrm{Ba}$(. . .6s6p $^{1}P_{1}$) atoms were carried out. An asymmetry observed by us and previously by Register et al. [Phys. Rev. A 28, 151 (1983)] has been explained using a model of scattering from a target with finite dimensions. This model employed coherence parameters which we calculated in the distorted-wave approximation. The results indicated that the interpretation of coherence experiments in terms of scattering from a pointlike target can lead to serious errors in the deduction of coherence parameters at low scattering angles.

DOI
10.1103/physreva.39.6022

Related papers

Electron impact coherence parameters for the (...6s5d1D2) to (...6s6p1P1) excitation in138Ba determined by superelastic scattering measurements

Y Li, P W Zetner

Superelastic electron scattering involving the de-excitation of laser-excited 138 Ba (...6s6p 1 P 1 ) to the lower-lying (...6s5d 1 D 2 ) metastable level has been investigated. These measurements have been used to extract the electron impact coherence parameters which describe excitation out of an isotropic (...6s5d 1 D 2 ) level to the higher-lying (...6s6p 1 P 1 ) state. Studies have been carried out for an electron impact energy of 20 eV and a range of scattering angles up to 45 degrees . This investigation represents a significant extension of coherence parameter measurements to inelastic transitions between excited atomic levels.

Journal of Physics B Atomic Molecular and Optical Physics•Dec 14, 1995•14 citations

Coherence Measurements for Excited to Excited State Transitions in Barium

Sandor Trajmar, I. Kanik, V. Karaganov +2 more

Experimental studies concerning elastic and inelastic electron scattering by coherently ensembles of Ba (...6s6p (sub 1)P(sub 1)) atoms with various degrees of alignment will be described. An in-plane, linearly-polarized laser beam was utilized to prepare these target ensembles and the electron scattering signal as a function of polarization angle was measured for several laser geometries at fixed impact energies and scattering angles. From these measurements, we derived cross sections and electron-impact coherence parameters associated with the electron scattering process which is time reverse of the actual experimentally studied process. This interpretation of the experiment is based on the theory of Macek and Herte. The experimental results were also interpreted in terms of cross sections and collision parameters associated with the actual experimental processes. Results obtained so far will be presented and plans for further studies will be discussed.

•Jan 1, 2000•0 citations

Influence of a finite scattering volume on the determination of electron-impact coherence parameters

P W Zetner, Sandor Trajmar, George Csanak

Superelastic electron scattering from laser-excited $^{138}\mathrm{Ba}$(. . .6s6p $^{1}$P) is investigated both theoretically and experimentally. The theoretical framework is developed and incorporated into a model of a realistic scattering geometry of finite spatial extent. Model calculations predict that the dependence of the superelastic scattering intensity on the linear polarization direction of the laser beam can be severely distorted due to the existence of a finite scattering volume. Our measurements confirm the presence of this distortion and are well described by the model calculations. Conclusions are drawn concerning the influence of this effect on the extraction of electron-impact coherence parameters.

Physical Review A•Jun 1, 1990•36 citations

Elastic electron scattering by laser-excited138Ba( ... 6s6p1P1) atoms

Sandor Trajmar, I. Kanik, M. A. Khakoo +4 more

The results of a joint experimental and theoretical study concerning elastic electron scattering by laser-excited 138 Ba( ... 6s6p 1 P 1 ) atoms are described. These studies demonstrate several important aspects of elastic electron collisions with coherently excited atoms, and are the first such studies. From the measurements, collision and coherence parameters, as well as cross sections associated with an atomic ensemble prepared with an arbitrary in-plane laser geometry and linear polarization (with respect to the collision frame), or equivalently with any magnetic sublevel superposition, have been obtained at 20 eV impact energy and at 10°, 15° and 20° scattering angles. The convergent close-coupling (CCC) method was used within the non-relativistic LS -coupling framework to calculate the magnetic sublevel scattering amplitudes. From these amplitudes all the parameters and cross sections at 20 eV impact energy were extracted in the full angular range in 1° steps. The experimental and theoretical results were found to be in good agreement, indicating that the CCC method can be reliably applied to elastic scattering by 138 Ba( ... 6s6p 1 P 1 ) atoms, and possibly to other heavy elements when spin-orbit coupling effects are negligible. Small but significant asymmetry was observed in the cross sections for scattering to the left and to the right. It was also found that elastic electron scattering by the initially isotropic atomic ensemble resulted in the creation of significant alignment. As a byproduct of the present studies, elastic scattering cross sections for metastable 138 Ba atoms were also obtained.

Journal of Physics B Atomic Molecular and Optical Physics•Jan 1, 1999•12 citations

Superelastic electron scattering from laser-excited174Yb(...6s6p 63P1)

Y Li, P W Zetner

Superelastic electron scattering from laser-excited 174 Yb is used to measure the L perpendicular to + electron impact coherence parameter for excitation of the 6 3 P 1 level at intermediate impact energies. This is the first application of the superelastic scattering technique to the determination of coherence parameters for excitation of an atomic level in which spin-orbit coupling plays a non-negligible role.

Journal of Physics B Atomic Molecular and Optical Physics•Jun 28, 1994•21 citations

New Data from Laser Interrogation of Electron-Atom Collisions Experiments

AT Masters, Robert T. Sang, W. R. MacGillivray +1 more

Recent data from two methods in which high resolution laser radiation is used to assist in determining electron-atom collision parameters are presented. The electron superelastic method has yielded the first measurement of Stokes parameters for electron de-excitation of the 32D5/2–32P3/2,1/2 transition of atomic Na, the upper level having been optically prepared by resonant, stepwise excitation from the 32S1/2 ground level via the 32P3/2 level using two single mode lasers. As well, we report on the development of a model to determine the optical pumping parameters for superelastic scattering from the 32P3/2 level when it is prepared by two lasers exciting from the F = 1 and F = 2 states respectively of the 32S1/ 2 ground level. Data are also presented for collision parameters for the excitation of the 61So–61 PI transition of the I = 0 isotope of Hg by electrons of 50 eV incident energy. The technique employed for these measurements is the stepwise electron–laser excitation coincidence method, in which the electron excited atom is further excited by resonant laser radiation, and fluorescence photons emitted by relaxation from the laser excited state are detected in coincidence with the scattered electron.

Australian Journal of Physics•Apr 1, 1996•1 citation
Measurements of superelastic scattering of electrons by laser-excited 138Ba^{138}\mathrm{Ba}138Ba(. . .6s6p 1P1^{1}P_{1}1P1​) atoms were carried out. An asymmetry observed by us and previously by Register et al. [Phys. Rev. A 28, 151 (1983)] has been explained using a model of scattering from a target with finite dimensions. This model employed coherence parameters which we calculated in the distorted-wave approximation. The results indicated that the interpretation of coherence experiments in terms of scattering from a pointlike target can lead to serious errors in the deduction of coherence parameters at low scattering angles.
Superelastic electron scattering involving the de-excitation of laser-excited 138 Ba (...6s6p 1 P 1 ) to the lower-lying (...6s5d 1 D 2 ) metastable level has been investigated. These measurements have been used to extract the electron impact coherence parameters which describe excitation out of an isotropic (...6s5d 1 D 2 ) level to the higher-lying (...6s6p 1 P 1 ) state. Studies have been carried out for an electron impact energy of 20 eV and a range of scattering angles up to 45 degrees . This investigation represents a significant extension of coherence parameter measurements to inelastic transitions between excited atomic levels.
Experimental studies concerning elastic and inelastic electron scattering by coherently ensembles of Ba (...6s6p (sub 1)P(sub 1)) atoms with various degrees of alignment will be described. An in-plane, linearly-polarized laser beam was utilized to prepare these target ensembles and the electron scattering signal as a function of polarization angle was measured for several laser geometries at fixed impact energies and scattering angles. From these measurements, we derived cross sections and electron-impact coherence parameters associated with the electron scattering process which is time reverse of the actual experimentally studied process. This interpretation of the experiment is based on the theory of Macek and Herte. The experimental results were also interpreted in terms of cross sections and collision parameters associated with the actual experimental processes. Results obtained so far will be presented and plans for further studies will be discussed.
Superelastic electron scattering from laser-excited 138Ba^{138}\mathrm{Ba}138Ba(. . .6s6p 1^{1}1P) is investigated both theoretically and experimentally. The theoretical framework is developed and incorporated into a model of a realistic scattering geometry of finite spatial extent. Model calculations predict that the dependence of the superelastic scattering intensity on the linear polarization direction of the laser beam can be severely distorted due to the existence of a finite scattering volume. Our measurements confirm the presence of this distortion and are well described by the model calculations. Conclusions are drawn concerning the influence of this effect on the extraction of electron-impact coherence parameters.
The results of a joint experimental and theoretical study concerning elastic electron scattering by laser-excited 138 Ba( ... 6s6p 1 P 1 ) atoms are described. These studies demonstrate several important aspects of elastic electron collisions with coherently excited atoms, and are the first such studies. From the measurements, collision and coherence parameters, as well as cross sections associated with an atomic ensemble prepared with an arbitrary in-plane laser geometry and linear polarization (with respect to the collision frame), or equivalently with any magnetic sublevel superposition, have been obtained at 20 eV impact energy and at 10°, 15° and 20° scattering angles. The convergent close-coupling (CCC) method was used within the non-relativistic LS -coupling framework to calculate the magnetic sublevel scattering amplitudes. From these amplitudes all the parameters and cross sections at 20 eV impact energy were extracted in the full angular range in 1° steps. The experimental and theoretical results were found to be in good agreement, indicating that the CCC method can be reliably applied to elastic scattering by 138 Ba( ... 6s6p 1 P 1 ) atoms, and possibly to other heavy elements when spin-orbit coupling effects are negligible. Small but significant asymmetry was observed in the cross sections for scattering to the left and to the right. It was also found that elastic electron scattering by the initially isotropic atomic ensemble resulted in the creation of significant alignment. As a byproduct of the present studies, elastic scattering cross sections for metastable 138 Ba atoms were also obtained.
Recent data from two methods in which high resolution laser radiation is used to assist in determining electron-atom collision parameters are presented. The electron superelastic method has yielded the first measurement of Stokes parameters for electron de-excitation of the 32D5/2–32P3/2,1/2 transition of atomic Na, the upper level having been optically prepared by resonant, stepwise excitation from the 32S1/2 ground level via the 32P3/2 level using two single mode lasers. As well, we report on the development of a model to determine the optical pumping parameters for superelastic scattering from the 32P3/2 level when it is prepared by two lasers exciting from the F = 1 and F = 2 states respectively of the 32S1/ 2 ground level. Data are also presented for collision parameters for the excitation of the 61So–61 PI transition of the I = 0 isotope of Hg by electrons of 50 eV incident energy. The technique employed for these measurements is the stepwise electron–laser excitation coincidence method, in which the electron excited atom is further excited by resonant laser radiation, and fluorescence photons emitted by relaxation from the laser excited state are detected in coincidence with the scattered electron.