AVS 50th International Symposium
    Vacuum Technology Wednesday Sessions
       Session VT-WeM

Paper VT-WeM2
Is Mass 19 in the Residual Gas of Very High Vacuum just F@super +@?

Wednesday, November 5, 2003, 8:40 am, Room 323

Session: Dynamic Vacuum Systems
Presenter: C.R. Cole, The College of William and Mary
Authors: C.R. Cole, The College of William and Mary
R.A. Outlaw, The College of William and Mary
R.L. Champion, The College of William and Mary
B.C. Holloway, The College of William and Mary
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Typically, the mass spectral peak observed at 19 amu in residual gas analyzers at very high vacuum has been solely attributed to fluorine. Using Fourier Transform Mass Spectrometry (FTMS), the presence of the hydronium ion, H@sub 3@O@super +@,has been fully resolved from F@super +@ and shown to be quite prevalent. Analysis is presented that shows that there is ample time for the formation of the hydronium ion through ion-molecule interactions and a direct correlation to the partial pressure of H@sub 2@O. The formation time and its correspondence to ionization, trap and resonance sequences have been characterized, as well as the gas collision formation mechanisms. Additionally, the generation of hydronium was further confirmed with D@sub 2@O experiments. Formation of D@sub 3@O@super +@ in a conventional quadrupole mass spectrometer has also been observed. Gas phase formation mechanisms of hydronium and deuteronium and other formation avenues, such as ESD, are discussed.