Method for trace oxygen detection

US5670378A · kind A · utility

Assignee

• The United States of America as represented by the Administrator of the National Aeronautics and Space Administration · US

Inventors

• Kin Fung Man · Arcadia, US
• Said Boumsellek · Fremont, US
• Ara Chutjian · La Cañada Flintridge, US

Key dates

• Filing date: Feb 23, 1995
• Grant date: Sep 23, 1997
• Expiry date: Feb 23, 2015

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10T436/24
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

Trace levels of molecular oxygen are measured by introducing a gas containing the molecular oxygen into a target zone, and impacting the molecular oxygen in the target zone with electrons at the O.sup.- resonant energy level for dissociative electron attachment to produce O.sup.- ions. Preferably, the electrons have an energy of about 4 to about 10 eV. The amount of O.sup.- ions produced is measured, and is correlated with the molecular oxygen content in the target zone. The technique is effective for measuring levels of oxygen below 50 ppb, and even less than 1 ppb. The amount of O.sup.- can be measure in a quadrupole mass analyzer. Best results are obtained when the electrons have an energy of about 6 to about 8 eV, and preferably about 6.8 eV. The method can be used for other species by selecting the appropriate electron energy level.