High-resolution total-cross-section measurements for electron scattering from Ar, Kr, and Xe employing a threshold-photoelectron source

M. Kurokawa, M. Kitajima, K. Toyoshima, T. Kishino, T. Odagiri, H. Kato, M. Hoshino, H. Tanaka, and K. Ito

Phys. Rev. A 84, 062717 – Published 29 December 2011

Abstract

Absolute total cross sections for electron scattering from Ar and Xe at electron energies ranging from 7 meV to 20 eV were obtained with the experimental technique employing the threshold-photoelectron source. The measured total cross sections are in good agreement with those obtained by other groups down to 100 meV, above which several experimental works have been reported. Scattering lengths for electron scattering from Ar, Kr, and Xe were determined from the present total cross sections and our recent results for Kr using the modified effective range theory. The values of the scattering length obtained in the present analysis differ from the values determined from the previous swarm experiments and beam experiments. The resonant structures in the total cross sections due to Feshbach resonances of Ar, Kr, and Xe with an improved energy resolution were also measured. Analyses of the resonant structure were carried out based on the spin-dependent resonant scattering theory in order to determine the values of the natural width of Feshbach resonances of Ar, Kr, and Xe precisely.

Received 25 October 2011

DOI:https://doi.org/10.1103/PhysRevA.84.062717

Authors & Affiliations

M. Kurokawa^1,*, M. Kitajima^1,†, K. Toyoshima¹, T. Kishino¹, T. Odagiri¹, H. Kato², M. Hoshino², H. Tanaka², and K. Ito³

¹Department of Chemistry, Tokyo Institute of Technology, Tokyo 152-8551, Japan
²Department of Physics, Sophia University, Tokyo 102-8554, Japan
³Photon Factory, Institute of Materials Structure Science, Tsukuba 305-0801, Japan

^*Present address: Central Research Laboratory, Hitachi Ltd., Tokyo 185-8601, Japan.
^†mkitajim@chem.titech.ac.jp

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Vol. 84, Iss. 6 — December 2011

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Figure 1
Cross section of the apparatus used in the present measurements. The photoionization cell and the first electrostatic lens system serve as the threshold-photoelectron source. A monochromatic photon beam at the first ionization threshold of Ar (15.760 eV) is introduced into the photoionization cell. The photoelectrons are collected by the penetrating field from the first lens system and formed into a beam. The energy of the electron beam is tuned by the second lens system and focused onto the collision cell filled with the target gas. The transmitted electrons are angular discriminated and refocused by the third lens system and detected by a channel electron multiplier. The results of the electron trajectory calculation at the collision energy of 0.1 eV are also shown.Reuse & Permissions
Figure 2
Total cross section for electron scattering from Ar (a) in the energy range up to 20 eV, and (b) in the energy range below 3 eV; $•$ indicates the present results. Also shown are experimental results of Gus'kov et al. [6], $⊲$ ; Jost et al. [46], $\circ$ ; Nickel et al. [45], $□$ ; Ferch et al. [7], $⋄$ ; Buckman and Lohmann [8], $▽$ ; Subramanian and Kumar [52], $△$ ; and Szmytkowski et al. [53], $⊳$ ; and theoretical results of Bell et al. [47], – $\cdot$ –; Yuan [48], $\dots$ ; Plenkiewicz et al. [49], – $\cdot$ $\cdot$ –; Mimnagh et al. [50], – –; and McEachran and Stauffer [51], — —.Reuse & Permissions
Figure 3
Total cross section for electron scattering from Xe (a) in the energy range up to 20 eV, and (b) in the energy range below 3 eV; $•$ indicates the present results. Also shown are experimental results of Gus'kov et al. [6], $⊲$ ; Jost et al. [46], $\circ$ ; Nickel et al. [45], $□$ ; Ferch et al. [54], $⋄$ ; Subramanian and Kumar [52], $△$ ; Alle et al. [57], $▽$ ; Szmytkowski et al. [53], $⊳$ ; and theoretical results of McEachran and Stauffer [55], — —; Sienkiewicz and Baylis [56], – $\cdot$ –; and Yuan and Zhang [58], $\dots$ .Reuse & Permissions
Figure 4
Total-cross-section curves derived from the MERT fits to the experimental total cross sections for electron scattering from rare-gas atoms. (a) Ar: present experimental data, $\circ$ ; MERT5 fit, - - - ; MERT5+ fit, — . (b) Kr: experimental data of Kurokawa et al. [25], $\circ$ ; MERT6 fit, - - -; MERT6+ fit, —. (c) Xe: present experimental data, $\circ$ ; MERT6 fit, - - -; MERT6+ fit, —.Reuse & Permissions
Figure 5
Experimental total cross sections for electron scattering from Ar, Kr, and Xe at around the Feshbach resonances. (a) The Ar $^{-}$ ( $3 p^{5} 4 s^{2}$ $^{2} P_{3 / 2}$ , $^{2} P_{1 / 2}$ ) resonances. (b) The Kr $^{-}$ ( $4 p^{5} 5 s^{2}$ $^{2} P_{3 / 2}$ , $^{2} P_{1 / 2}$ ) resonances. (c) The Xe $^{-}$ ( $5 p^{5} 6 s^{2}$ $^{2} P_{3 / 2}$ , $^{2} P_{1 / 2}$ ) resonances. Vertical bars represent the energy position corresponding to the Feshbach resonances and the exited states of the neutral atom.Reuse & Permissions
Figure 6
Profiles of the cross sections due to the Feshbach resonances, $σ_{res}^{\exp} (E)$ (open circles), and the best fits for the resonant cross sections obtained by fitting the calculated $σ_{res}^{att} (E)$ (solid curves); (a) the Ar $^{-}$ ( $3 p^{5} 4 s^{2}$ $^{2} P_{3 / 2}$ ) and the Ar $^{-}$ ( $3 p^{5} 4 s^{2}$ $^{2} P_{1 / 2}$ ) resonances, (b) the Kr $^{-}$ ( $4 p^{5} 5 s^{2}$ $^{2} P_{3 / 2}$ ) resonance, and (c) the Xe $^{-}$ ( $5 p^{5} 6 s^{2}$ $^{2} P_{3 / 2}$ ) resonance.Reuse & Permissions

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