METHOD FOR DETERMINING A GAS CONCENTRATION IN A GAS MIXTURE AND DEVICE THEREFOR

摘要

The invention concerns a method for determining the relative concentration of a molecular gas in a gas mixture of at least two types of molecules not exhibiting spherical rotational inertia. The invention is characterised in that it consists in: emitting at least two pulses respectively of two light beams from a laser delivering sub-picosecond pulses, at least a probe beam and at least a pump beam so that each pulse of the probe beam is temporally offset relative to each pulse of the pump beam; then polarising the pump beam along a particular direction A and the probe beam along a direction theta relative to the direction A; then passing the pump and probe beams through a cell containing the gas mixture in an optical Kerr effect arrangement, then measuring the intensity of the probe beam signal at the cell output, after a so-called analyzing polarizer; and finally calculating the relative concentration of a gas relative to another on the basis of the measurement of the intensity of the probe beam signal.