Direct Measurement of the Two-Photon Excitation Cross-Section of Xenon by Laser Absorption

Laser diagnostics in plasmas frequently uses the so-called TALIF technique, which consists in recording the fluorescence following the two-photon excitation of an atomic species. For oxygen density measurements, a widespread protocol is to compare the fluorescence yield to that measured in Xe vapor, the density of which can be known straightforwardly, when illuminated by the same optical system. This comparison is easily done because we can find energy levels for these two atoms, where the excitation and fluorescence wavelengths are spectrally close. However, quantitative analysis relies on knowledge of the ratio of the two two-photon cross-sections
$\sigma^{(2)}$
involved [1]. We present a direct measurement of the integrated cross-section
$\sigma^{(2)}(\mathrm{X}\mathrm{e})$
of xenon that therefore appeared quite desirable.