Sensitive and interference-immune formaldehyde diagnostic for high-temperature reacting gases using two-color laser absorption near 5.6 µm

In this work we present a novel two-color differential absorption diagnostic near 5.6 μm using an external-cavity quantum-cascade-laser (EC-QCL) for formaldehyde (CH2O) detection in high-temperature reacting gases. This diagnostic utilizes the narrow mid-infrared absorption features of CH2O in the R branch of the C=O stretching band. Specifically, the online and offline colors were chosen as 1787.05 cm-1 and 1787.85 cm-1, respectively. Compared...