title: Investigation of two-photon-induced polarization spectroscopy of the a-X (1,0) transition in molecular nitrogen at elevated pressures.
abstract: Two-photon-induced polarization spectroscopy of molecular nitrogen in the alpha 1IIg(nu' =) <-- X 1Sigma(g)+ (nu" =) system near 283 nm was performed, and its signal dependence investigated over the pressure range from 1.2 to 5 bars at 300 K. A significant increase of the signal intensity with pressure beyond the expected square law for a two-photon process was observed for pure nitrogen. Similar behavior was also found for a constant nitrogen partial pressure with increasing partial pressures of argon buffer gas. In both cases the spectral linewidth of the excited transitions increased dramatically with overall pressure. A possible explanation is given for the observed behavior in terms of contributions to the nonlinear susceptibility of the medium from the population of one-photon resonantly absorbing excited-state nitrogen and ground state N(2)(+) ions created in the multiphoton absorption process at the high laser intensities required.
authors.affiliation: Division of Combustion Physics, Lund Institute of Technology, Box 118, S-22100 Lund, Sweden. clemens.kaminski@forbrf.lth.se
authors.forename: C F
authors.initials: CF
authors.lastname: Kaminski
authors.forename: T
authors.initials: T
authors.lastname: Dreier