Distortion of infrared picosecond pulses after propagation in atmospheric air

Significant pulse distortion of infrared pulses is observed at frequencies where gaseous components of air have resonant transitions. For instance, coherent interaction with absorption lines of water vapor between 6 and 8 μm gives drastic effects after a pulse propagation as short as 80 cm. Experimental data are compared with model calculations in the small area pulse limit. A dephasing time of T2=50 ps is found for a rovibrational transition at ν̃=1576.2 cm−1 at atmospheric pressure.