Application of time-resolved spectroscopy to concentration measurements in gas mixtures

Concentration measurements using femtosecond Raman Induced Polarization Spectroscopy (RIPS) are performed in binary gas mixtures CO₂–N₂ and CO₂–N₂O at room temperature. The principle of these measurements is based on the nonlinear rotational time response of each molecular component of the mixture. The general form of this molecular response is a series of periodic transients with a period related to the rotational constant B_e. The relative strength of the individual responses allows an accurate determination of the concentration. Two techniques are presented using either two pulses (one pump and one probe) or three pulses (two pumps and one probe).