Physical Review A

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

Published Jul 17, 2001• 8 citations

Abstract

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.

DOI: 10.1103/physreva.64.022716

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Physical Review A

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

Published Jul 17, 2001• 8 citations

Publisher

Abstract

{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.

DOI: 10.1103/physreva.64.022716

Related papers

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Physical Review AOct 1, 200231 citations

{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.

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.

Our Dirac R-matrix calculations suggest that none of the heavy alkali-metal negative ions, Rb, Cs, and Fr, has an excited bound state. Their lowest excited state appears to be a multiplet of

{}^{3}{P}_{J}^{o}

-shape resonances, the

J=1

component of which was recently observed in photodetachment experiments on ${\mathrm{Cs}}^{\ensuremath{-}}.$ We analyze these

{}^{3}{P}_{J}^{o}

and the

{}^{3}{S}^{e}

excited negative ion states in partial and converged total scattering cross sections for slow electrons with incident kinetic energies below 120 meV. Our results are in excellent agreement with available experimental data. We also propose a new value for the electron affinity of Fr, provide the scattering length for electronic collisions with Rb, Cs, and Fr, and discuss the nuclear charge dependence of relativistic effects in the resonance profiles.

We report on a theoretical and experimental study of state-selective differential single-electron transfer cross sections between

{\mathrm{Na}}^{+}

ions and

\mathrm{Rb}(5s,5p)

atoms at collision energies of 2, 5, and 7 keV. A two-center multichannel semiclassical impact parameter close-coupling method with straight-line trajectories was used to obtain single-electron capture amplitudes. By combining with the eikonal approximation, we calculated the angular differential cross sections. These results are compared to the experimental data obtained with Rb targets cooled in a magnetic optical trap. It is shown that there is generally a good agreement between the present calculations and the experiments. In spite of the higher resolution offered from the cold target, the rapid oscillations in the differential cross sections are not resolved by the experiments.