The effect of temperature correction on the measured thickness of formaldehyde zones in diffusion flames for 355 nm excitation

The temperature dependent corrections of the formaldehyde laser induced fluorescence raw signal are discussed for the 355 nm excitation, which is widely available as the third harmonic of Nd-YAG lasers. The temperature dependence of the HCHO partition function is calculated explicitly and the effect of quenching corrections is discussed in view of the absence of experimental data on collision cross-sections. Particular reference is made to the case of HCHO layers in hydrocarbon diffusion flames. It is shown that the thickness of such layers is not affected drastically by the calculated corrections, which has implications for the estimate of the scalar dissipation rate in diffusion flames.