Electron impact ionization of the NF3 molecule

V. Tarnovsky, A. Levin, K. Becker, R. Basner, M. Schmidt

Research output: Contribution to journalArticlepeer-review

Abstract

We report measurements of the absolute cross sections for the electron-impact ionizaton of the NF3 molecule from threshold to 200 eV. Absolute values and shapes for the NF3 parent ionization cross section were obtained independently in two different laboratories using two different experimental techniques. The agreement was better than ±8%. At 70 eV, the absolute parent NF3 ionization cross section is 0.35 ± 0.06 Å2. The dissociative ionization of NF3 was studied primarily using the fast-beam technique. Absolute cross sections for the formation of the fragment ions NF+2 and NF+ were found to be 1.05 ± 0.20 Å2 (NF+2) and 0.7 ± 0.15 Å2 (NF+ at 70 eV. Two channels contribute to the observed NF+ ion signal, the single positive ion formation NF3 → NF+ + 2F and the positive ion pair formation NF3 → NF+ + F+ + F with an appearance energy of 36.5 ± 1.0 eV. While the NF+2 fragment ions are formed with little excess kinetic energy for impact energies near threshold, the NF+ fragment ions are formed with a broad distribution of excess kinetic energies ranging from essentially zero to about 4 eV. Cross sections for the formation of the atomic fragment ions F+ and N+ were found to be small with a maximum value of 0.3 Å2 for F+ (at 70 eV) which can be attributed primarily to the double positive ion formations NF3 → NF+ + F+ + F. The upper limit for the N+ cross section from NF3 is 0.1 Å2 at 70 eV.

Original languageEnglish (US)
Pages (from-to)175-185
Number of pages11
JournalInternational Journal of Mass Spectrometry and Ion Processes
Volume133
Issue number2-3
DOIs
StatePublished - May 19 1994

Keywords

  • Cross sections
  • Electron impact ionization
  • Plasma processing

ASJC Scopus subject areas

  • Spectroscopy

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