Investigation of two-photon-induced polarization spectroscopy of the a–X (1,0) transition in molecular nitrogen at elevated pressures

Clemens F. Kaminski, Thomas Dreier
2000 Applied Optics  
Two-photon-induced polarization spectroscopy of molecular nitrogen in the a 1 ⌸ g ͑Ј ϭ 1͒ 4 X 1 ⌺ g ϩ ͑Љ ϭ 0͒ 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
more » ... l 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 ϩ ions created in the multiphoton absorption process at the high laser intensities required.
doi:10.1364/ao.39.001042 pmid:18337983 fatcat:ndt32drut5dj7e3fmqc5krvcbi