Temperature measurements in flames using water molecule overtone spectra detected by intracavity laser absorption spectroscopy

Overtone absorption spectra of water molecules were recorded with intracavity laser absorption spectroscopy (ICLAS) based on a Ti:Sapphire laser with atmospheric pressure methane/air or hydrogen/air flame was placed into the cavity of the Ti:Sapphire laser. Though the flame occupied a small part of the cavity, substantial changes in the water spectrum were observed and new lines appeared. This suggests the possibility of measuring temperature in flames using an ICLAS spectrum of the water. Computer simulations based on the water spectrum lines assigned in the literature showed that a sensitivity of about ten degrees can be expected. The use of lines with higher rotational quantum numbers could substantially improve the sensitivity.