N2 rotational temperature analysis by laser induced fluorescence following resonant enhanced multiphotonion ization

It has been demonstrated that the rotational temperature of molecular nitrogen at atmospheric pressure can be determined by direct optical probing of the N₂ (X, v=3D0) ground state with subsequent analysis of the rotational state distribution. A tunable probe laser was scanned over resonant enhanced multi-photon ionization transitions initiating from various N₂ (X, v=3D0, J) states. At atmospheric pressure, the laser photo-ionization also induced nitrogen fluorescence bands. Analysis of the relative fluorescence as a function of laser wavelength produced a calculated N₂ (X, v=3D0, J) rotation state distribution and the assignment of a rotational temperature.