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Gernot Friedrichs, H.Gg. Wagner

Quantitative FM Spectroscopy at High Temperatures: The Detection of ¹CH₂ behind Shock Waves

The technique of time resolved frequency modulation (FM) spectroscopy has been shown to provide a very sensitive means to detect small radicals behind shock waves. Features of high temperature FM spectroscopy behind shock waves will be discussed and a general signal conversion procedure to carry out quantitative concentration measurements will be presented.
Using a high modulation frequency, a high modulation index and high total optical power, singlet methylene radicals (¹CH₂) have been detected behind shock waves for the first time. For a pressure of 1 bar the narrow bandwidth absorption coefficient of ¹CH₂ at 590.707 nm (b¹B₁(0,14,0)4₀₄ ← ã¹A₁(0,0,0)4₁₄) was determined in the temperature range 1900-2800 K to be:

α_c /(cm² mol^-1) = -6.16 × 10⁵ + ((2.597 × 10⁹) : (T/K)) - ((1.181 × 10¹²) : (T/K)²).

Zeitschrift für Physikalische Chemie, Oldenbourg Wissenschaftsverlag

Print ISSN: 0942-9352
Volume: 214, 12/2000
Pages: 1723

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