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

G. Friedrichs and H.Gg. Wagner
Z. Phys. Chem. 214, 1723-1746 (2000)

 

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 (^1CH_2) have been detected behind shock waves for the first time. For a pressure of 1 bar the narrow bandwidth absorption coefficient of  ^1CH_2 at 590.707 nm (\tilde{b}1B1(0,14,0)404 <= \tilde{a}1A1(0,0,0)414) was determined in the temperature range 1900 - 2800 K to be:

αc / (cm2mol-1) = -6.16·105 + 2.597·109 / (T/K) - 1.181·1012 / (T/K)2

 

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