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

Journal of Physics B Atomic and Molecular Physics

Scattering of electrons by Cs atoms at low energies

W. Gehenn, E. Reichert

Published Oct 21, 1977• 34 citations
Publisher

Abstract

Electrons are scattered elastically by caesium atoms in a crossed-beam experiment. The dependence of the cross section on collision energy and scattering angle has been measured; the collision energies studied are in the range from 0.8 to 20 eV. Resonant structures are observed in the elastic cross section at an energy of 1.49 eV and around the 6 2 P 1/2 threshold at 1.39 eV. It is believed that the 1.49 eV resonance is due to an autoionising F state of Cs - which is consistent with theoretical predictions. The angular distributions of the elastic cross section agree satisfactorily with theory for collision energies below 2 eV. At higher energies larger deviations from theory are observed.

DOI
10.1088/0022-3700/10/15/019

Related papers

Effects of ultra-low-energy resonances in the elastic scattering of electrons by alkali-metal atoms in collisions of high-Rydberg atoms with alkali-metal atoms

Michio Matsuzawa, Naoto Koyama

It is theoretically predicted that an isolated narrow resonance in the elastic scattering of electrons by alkali-metal atoms (M) gives rise to a single maximum in the n dependence of the total cross sections of high-Rydberg atoms A** in the highest allowed angular momentum states with M if the resonance width is roughly equal to or larger than the width of a single peak of the electron momentum distribution of the Rydberg states with highest angular momentum, i.e. l=n-1. This can be used to detect the narrow resonance theoretically predicted in e-M elastic scattering at ultra-low energies.

Journal of Physics B Atomic and Molecular Physics•May 28, 1985•4 citations

LOW ENERGY ELECTRON SCATTERING FROM ALKALI METAL VAPORS

A. R. Johnston

Two techniques have been used to study low energy electron scattering processes in the alkali metals. A transmission experiment was used to search for resonance structure in the total scattering cross section of sodium, potassium, rubidium, and cesium. A shape resonance was observed in sodium at 0.08 (+OR-) 0.03 eV. In rubidium, evidence was found for the existence of a shape resonance below 0.05 eV. No shape resonance structure was observed in potassium or cesium for energies above 0.1 eV. For energies near the first excited state to near the lowest ionization potential, a progression of Feshbach resonances was observed in each atom. The graphical analysis technique of Spence was used to group most of these resonances into seven families. An analysis is given of the mechanisms affecting the rejection of scattered electrons in the transmission spectrometer. A quantitative description of two modes of operation of the spectrometer is presented. The second portion of this dissertation concerns the measurement of the near-threshold excitation and ionization cross sections in sodium, potassium, and rubidium. A trapped-electron experiment was used to make a relative measurement of these cross sections. The shapes of the excitation cross sections are, in general, somewhat different from other experimental work but are in good agreement with the close-coupling calculations of Moores and Norcross. The shapes of the ionization cross sections are in reasonable agreement with previous work. The ratio of the excitation cross section at 2.5 eV in sodium, 2.0 eV in potassium, and 1.8 eV in rubidium to the respective ionization cross section at the first peak was measured and found to be 3.9 (+OR-) 13% in Na, 5.8 (+OR-) 10% in K, and 6.4 (+OR-) 13% in Rb. These ratios are generally larger than those derived from independent values of the individual cross sections. An analysis of several systematic effects associated with the measurement of the cross section ratio was made. Results from this analysis were used to correct the measured excitation cross section for effects of the elastically scattered electrons.

•Jan 1, 1983•0 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

Angle-differential and momentum-transfer cross sections for e−+Rb, Cs, and Fr collisions at low energies: 3Fo shape resonances in Rb−, Cs−, and Fr− ions

Cristian Bahrim, Uwe Thumm

Based on the relativistic Dirac R-matrix method, we calculate angle-dependent and momentum-transfer cross sections for electron scattering by Rb, Cs, and Fr atoms at impact energies below 3 eV. Our results for momentum transfer for ${e}^{\ensuremath{-}}+\mathrm{Rb}$ and Cs collisions are compared with available data from swarm experiments. We find clear evidence for a ${\mathrm{Cs}}^{\ensuremath{-}}{(}^{3}{F}^{o})$ shape resonance at 1.528 eV, in excellent agreement with angle-dependent electron-scattering measurements. We analyze and compare the ${}^{3}{F}^{o}$ shape resonance in ${e}^{\ensuremath{-}}+\mathrm{Rb},$ Cs, and Fr elastic collisions.

Physical Review A•Jul 17, 2001•8 citations

Total cross sections for electron scattering from He and Ne at very low energies

K. Shigemura, M. Kitajima, M. Kurokawa +7 more

Absolute total cross sections for electron scattering from He and Ne are obtained in the energy range from 20 eV down to below 10 meV with a very narrow electron energy width of 6--8 meV using the threshold-photoelectron source. Total cross sections obtained in the present study generally agree well with those obtained in the previous experiments for both He and Ne above 100 meV, where several experimental works have been reported. Comparison of the present cross sections with the theoretical cross sections which have been regarded as the ``standard'' cross sections shows very good agreement even at very low energies below 10 meV, which confirms the validity of theoretical cross sections. The scattering lengths for electron scattering from He and Ne are also determined from the present total cross sections using the modified effective range theory. The resonant structures in the total cross sections due to Feshbach resonances of He and Ne are also observed. Analysis of the resonant structure was carried out based on the spin-dependent resonant scattering theory in order to determine the values of natural width of Feshbach resonance of Ne.

Physical Review A•Feb 21, 2014•22 citations

Negative-ion resonances in cross sections for slow-electron–heavy-alkali-metal-atom scattering

Cristian Bahrim, Uwe Thumm, I. I. Fabrikant

We analyze negative-ion resonances in elastic and inelastic total scattering cross sections for slow electron collisions with the heavy-alkali-metal atoms Rb, Cs, and Fr. Our calculations are based on the Dirac $R$-matrix method [Thumm and Norcross, Phys. Rev. A 45, 6349 (1992)]. For incident electrons of up to 2.8 eV kinetic energy, we compare a ${}^{3}{P}^{o}$ shape resonance and ${}^{3}{P}^{e},$ ${}^{1}{P}_{1}^{o},$ and ${}^{1}{D}_{2}^{o}$ Feshbach resonances, located below the first excitation threshold of the atomic target in the low-lying spectra of the ${\mathrm{Rb}}^{\ensuremath{-}},$ ${\mathrm{Cs}}^{\ensuremath{-}},$ and ${\mathrm{Fr}}^{\ensuremath{-}}$ negative ions, with available experimental data and other calculations. We provide the resonance parameters, partial and converged total elastic and inelastic scattering cross sections, and discuss the relative importance of relativistic effects for the three heavy-alkali-metal targets.

Physical Review A•Mar 19, 2001•36 citations
Electrons are scattered elastically by caesium atoms in a crossed-beam experiment. The dependence of the cross section on collision energy and scattering angle has been measured; the collision energies studied are in the range from 0.8 to 20 eV. Resonant structures are observed in the elastic cross section at an energy of 1.49 eV and around the 6 2 P 1/2 threshold at 1.39 eV. It is believed that the 1.49 eV resonance is due to an autoionising F state of Cs - which is consistent with theoretical predictions. The angular distributions of the elastic cross section agree satisfactorily with theory for collision energies below 2 eV. At higher energies larger deviations from theory are observed.
It is theoretically predicted that an isolated narrow resonance in the elastic scattering of electrons by alkali-metal atoms (M) gives rise to a single maximum in the n dependence of the total cross sections of high-Rydberg atoms A** in the highest allowed angular momentum states with M if the resonance width is roughly equal to or larger than the width of a single peak of the electron momentum distribution of the Rydberg states with highest angular momentum, i.e. l=n-1. This can be used to detect the narrow resonance theoretically predicted in e-M elastic scattering at ultra-low energies.
Two techniques have been used to study low energy electron scattering processes in the alkali metals. A transmission experiment was used to search for resonance structure in the total scattering cross section of sodium, potassium, rubidium, and cesium. A shape resonance was observed in sodium at 0.08 (+OR-) 0.03 eV. In rubidium, evidence was found for the existence of a shape resonance below 0.05 eV. No shape resonance structure was observed in potassium or cesium for energies above 0.1 eV. For energies near the first excited state to near the lowest ionization potential, a progression of Feshbach resonances was observed in each atom. The graphical analysis technique of Spence was used to group most of these resonances into seven families. An analysis is given of the mechanisms affecting the rejection of scattered electrons in the transmission spectrometer. A quantitative description of two modes of operation of the spectrometer is presented. The second portion of this dissertation concerns the measurement of the near-threshold excitation and ionization cross sections in sodium, potassium, and rubidium. A trapped-electron experiment was used to make a relative measurement of these cross sections. The shapes of the excitation cross sections are, in general, somewhat different from other experimental work but are in good agreement with the close-coupling calculations of Moores and Norcross. The shapes of the ionization cross sections are in reasonable agreement with previous work. The ratio of the excitation cross section at 2.5 eV in sodium, 2.0 eV in potassium, and 1.8 eV in rubidium to the respective ionization cross section at the first peak was measured and found to be 3.9 (+OR-) 13% in Na, 5.8 (+OR-) 10% in K, and 6.4 (+OR-) 13% in Rb. These ratios are generally larger than those derived from independent values of the individual cross sections. An analysis of several systematic effects associated with the measurement of the cross section ratio was made. Results from this analysis were used to correct the measured excitation cross section for effects of the elastically scattered electrons.
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.
Based on the relativistic Dirac R-matrix method, we calculate angle-dependent and momentum-transfer cross sections for electron scattering by Rb, Cs, and Fr atoms at impact energies below 3 eV. Our results for momentum transfer for ${e}^{\ensuremath{-}}+\mathrm{Rb}$ and Cs collisions are compared with available data from swarm experiments. We find clear evidence for a ${\mathrm{Cs}}^{\ensuremath{-}}{(}^{3}{F}^{o})$ shape resonance at 1.528 eV, in excellent agreement with angle-dependent electron-scattering measurements. We analyze and compare the 3Fo{}^{3}{F}^{o}3Fo shape resonance in ${e}^{\ensuremath{-}}+\mathrm{Rb},$ Cs, and Fr elastic collisions.
Absolute total cross sections for electron scattering from He and Ne are obtained in the energy range from 20 eV down to below 10 meV with a very narrow electron energy width of 6--8 meV using the threshold-photoelectron source. Total cross sections obtained in the present study generally agree well with those obtained in the previous experiments for both He and Ne above 100 meV, where several experimental works have been reported. Comparison of the present cross sections with the theoretical cross sections which have been regarded as the ``standard'' cross sections shows very good agreement even at very low energies below 10 meV, which confirms the validity of theoretical cross sections. The scattering lengths for electron scattering from He and Ne are also determined from the present total cross sections using the modified effective range theory. The resonant structures in the total cross sections due to Feshbach resonances of He and Ne are also observed. Analysis of the resonant structure was carried out based on the spin-dependent resonant scattering theory in order to determine the values of natural width of Feshbach resonance of Ne.
We analyze negative-ion resonances in elastic and inelastic total scattering cross sections for slow electron collisions with the heavy-alkali-metal atoms Rb, Cs, and Fr. Our calculations are based on the Dirac RRR-matrix method [Thumm and Norcross, Phys. Rev. A 45, 6349 (1992)]. For incident electrons of up to 2.8 eV kinetic energy, we compare a 3Po{}^{3}{P}^{o}3Po shape resonance and 3Pe,{}^{3}{P}^{e},3Pe, 1P1o,{}^{1}{P}_{1}^{o},1P1o​, and 1D2o{}^{1}{D}_{2}^{o}1D2o​ Feshbach resonances, located below the first excitation threshold of the atomic target in the low-lying spectra of the ${\mathrm{Rb}}^{\ensuremath{-}},$ ${\mathrm{Cs}}^{\ensuremath{-}},$ and ${\mathrm{Fr}}^{\ensuremath{-}}$ negative ions, with available experimental data and other calculations. We provide the resonance parameters, partial and converged total elastic and inelastic scattering cross sections, and discuss the relative importance of relativistic effects for the three heavy-alkali-metal targets.