Method and apparatus for contactless acquisition of data for the locally resolved determination of the density and temperature in a measurement volume

An apparatus for contactless acquisition of data for determining at least one of the parameters density and temperature of a molecular gas within a predetermined volume, said gas containing molecules which collide with each other with a predetermined collision frequency, said apparatus comprising:

• (a) laser means for generating and directing laser radiation through said volume, said laser radiation containing at least one wavelength adapted to excite a molecular transition of the molecules to produce excited molecules;
• (b) optical means for measuring the absorption of said excited molecules during a period of time after said excitation which is short compared with the reciprocal collision frequency.

An apparatus for contactless acquisition of data for determining at least one of the parameters density and temperature of a molecular gas within a predetermined volume, said gas containing molecules which collide with each other with a predetermined collision frequency, said apparatus comprising:

• (a) laser means for generating and directing laser radiation through said volume, said laser radiation containing at least one wavelength adapted to excite a molecular transition of the molecules to produce excited molecules;
• (b) means for measuring the intensity of fluorescence radiation emitted by said excited molecules during a period of time after said excitation which is short compared with the reciprocal collision frequency.