Emission noise spectrum in a premixed H2-O2-N2 flame

Abstract

Experimental noise spectra in the frequency range of 15–105 Hz are reported for the thermal emission of the first resonance doublet of Na and K in a premixed H2-O2-N2 flame, and for the flame background emission. Under certain conditions, low-frequency peaks arise in the noise spectrum below 100 Hz, while a minimum is found at about 3 kHz. This minimum is of interest with respect to the optimal modulation frequency in atomic fluorescence measurements. The possible sources of fluctuations are discussed, but definite conclusions cannot yet be drawn.