Measurement of collisional multiphoton energy deposition by a new optothermal detector

The infrared multiphoton absorption of SF₆ under collisional condition has been measured by a new optothermal detector which is based on measuring the change of resistance of a platinum filament. The optothermal signal, i.e., the absorbance of CO₂ laser energy by SF₆, was enhanced by the addition of Ar or NH₃. But the increase of optothermal signal caused by adding NH₃ is much greater than that caused by adding Ar, mainly due to the energy siphoning from excited SF₆ molecules to NH₃ molecules.