- Author
- Smyth, K. C. | Tjossem, P. J. H.
- Title
- Signal Detection Efficiency in Multiphoton Ionization Flame Measurements.
- Coporate
- National Institute of Standards and Technology, Gaithersburg, MD
- Journal
- Applied Optics, Vol. 29, No. 33, 4891-4898, November 20, 1990
- Keywords
- signal detection | ionization | laminar flames | diffusion flames | atmospheric pressure | carbon monoxide | argon
- Abstract
- Multiphoton ionization is often the most sensitive method available for detecting radical species in flame environments. To make accurate relative concentration measurements, however, the electron (or ion) detection efficiency as a function of flame position must be known. Two methods are presented for determining this quantity in a laminar CH4/air diffusion flame burning at atmospheric pressure: (1) simultaneous detection of ionization and fluorescence in CO, following two-photon excitation of the [equation] state at 230.0 nm; (2) comparison of 3 + 1 multiphoton ionization of the 4s' state of argon at 314.4 nm with mass spectrometric measurements. The results show significant variation of the electron detection efficiency in the lean, stoichiometric, and rich flame regions, with the greatest detection sensitivity observed in the high-temperature, primary reaction zones (i.e., near stoichiometric conditions). Corrections to multiphoton ionization data obtained for H atoms are discuseed in terms of determining relative concentration profiles across the methane/air diffusion flame.