Investigation of two-photon-induced polarization spectroscopy of the a-X (1,0) transition in molecular nitrogen at elevated pressures |
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Authors: | Kaminski C F Dreier T |
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Affiliation: | Division of Combustion Physics, Lund Institute of Technology, Box 118, S-22100 Lund, Sweden. clemens.kaminski@forbrf.lth.se |
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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. |
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