1CH and CH2O in Atmospheric Pressure Methane/Air Bunsen Flames

Abstract: Laser-induced fluorescence of CH B2Σ-v’=1 is excited in atmospheric pressure Bunsen flames using rotational levels above and below the predissociation limit. There is significant rotational, vibrational, and electronic energy transfer even when levels above the predissociation limit are excited. At atmospheric pressure rotational energy transfer produces a variation in the fluorescence quantum yield with rotational level and gas temperature. Laser-induced fluorescence of CH2O exciting A-X 41 0 allows formaldehyde detection at an excitation wavelength quite near (and often overlapped) with the CH B-X (1,0). The formaldehyde structure is contained inside the CH in the premixed inner cone of the Bunsen flame. Excitation of CH2O A-X 41 0 provides an LIF strategy that minimizes the variation of the population of the excited level over the 700-1800 K temperature range important in the flame. 1