Methods for measuring absolute cross sections of electron impact excitation out of the metastable levels of He and Ar

Journal Article · Wed May 01 04:00:00 EDT 1996 · Bulletin of the American Physical Society

OSTI ID:394332

Lagus, M E; Boffard, J B; Piech, G A ^[1]

---

1. Univ. of Wisconsin, Madison, WI (United States); and others

The comprehensive study of electron excitation out of metastable levels requires measuring cross sections into numerous levels over a broad energy range. The authors describe two different apparatus used to measure cross sections for electron excitation out of the metastable levels of He and Ar. The first apparatus uses a hollow cathode discharge as its source of metastable atoms (n {approximately} 10{sup 9} cm{sup {minus}3}), and it is calibrated using a laser induced fluorescence (LIF) technique. This apparatus is most suitable for measuring relative cross sections at energies below the threshold for ground state excitation. To extend the measurements to high energies the second apparatus uses charge exchange of a He{sup +} (or Ar{sup +}) ion beam with cesium to produce primarily metastable beams of He (or Ar) with a n {approximately} 10{sup 6} cm{sup {minus}3}. A thermal detector, calibrated with ions, is used to measure the metastable beam flux. This along with direct measurements of the spatial distributions of the metastable and electron beam allows the authors to measure absolute cross sections. The principles and methods of measurements are described in detail.

• OSTI ID: 394332
• Report Number(s): CONF-9605105--
• Journal Information: Bulletin of the American Physical Society, Journal Name: Bulletin of the American Physical Society Journal Issue: 3 Vol. 41; ISSN BAPSA6; ISSN 0003-0503
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
ARGON
COULOMB EXCITATION
CROSS SECTIONS
ELECTRON-ATOM COLLISIONS
HELIUM
METASTABLE STATES