Spatially resolved trace detection of HCl in flames with mid-infrared polarization spectroscopy.

Sensitive and nonintrusive detection of HCl in reactive gas flows with high spatial and temporal resolution manner has for the first time (to our knowledge) been demonstrated using mid-infrared polarization spectroscopy (IRPS). Trace levels of HCl were prepared in an atmospheric pressure premixed CH4/O2/Ar flat flame by seeding a small amount of chloroform into the Ar flow. Detection of HCl with IRPS in the burnt region of the stoichiometric flame was performed by probing the fundamental ro-vibration transitions with a 3.2 microm tunable pulsed laser. The quantitative nature, the detection sensitivity, and the potential spectral interferences from water were investigated.