A system (1) for determining the characteristics of a gas is described, comprising at least one beam (10) of coherent and monochromatic light, detecting means (20) of scattered light comprising at least one photo-detector (21), at least one measuring chamber (30) within which the beam (10) and the detecting means (20) are operating, and control means (40) operatively connected to the photo-detector (21) for recording an amount of scattered light according to the Rayleigh scattering principle depending on the physical characteristics of the gas molecule and on a wavelength of the coherent and monochromatic light, the beam (10) of coherent and monochromatic light being emitted by at least one laser (11) with continuous wave. A method for measuring the characteristics of a gas through such system (1) is further described.
