The anomalous shape of the cross section for the formation of SF3+ fragment ions produced by electron impact on SF6 revisited

S Feil; K Gluch; P Scheier; K Becker; T D Märk

doi:10.1063/1.1753553

The anomalous shape of the cross section for the formation of SF3+ fragment ions produced by electron impact on SF6 revisited

J Chem Phys. 2004 Jun 22;120(24):11465-8. doi: 10.1063/1.1753553.

Authors

S Feil¹, K Gluch, P Scheier, K Becker, T D Märk

Affiliation

¹ Institut für Ionenphysik, Leopold Franzens Universität, Technikerstrasse 25, A-6020 Innsbruck, Austria.

PMID: 15268180
DOI: 10.1063/1.1753553

Abstract

The partial ionization cross section for the formation of SF(3) (+) fragment ions following electron impact on SF(6) is known to have a pronounced structure in the cross section curve slightly above 40 eV. We used the mass-analyzed ion kinetic energy (MIKE) scan technique to demonstrate the presence of a channel contributing to the SF(3) (+) partial ionization cross section that we attribute to the Coulomb explosion of doubly charged metastable SF(4) (2+) ions into two singly charged ions SF(3) (+) and F(+), with a threshold energy of about 45.5 eV. Thus the observed unusual shape of the SF(3) (+) partial ionization cross section is the result of two contributions, (i) the direct formation of SF(3) (+) fragment ions via dissociative ionization of SF(6) with a threshold energy of 22 eV and (ii) the Coulomb explosion of metastable SF(4) (2+) ions with a threshold energy of about 45.5 eV. A detailed analysis of the MIKE spectrum reveals an average kinetic energy release of about 5 eV in the Coulomb explosion of the SF(4) (2+) ions with evidence of a second channel corresponding to an average kinetic energy release of about 1.1 eV.