Absolute calibration of atomic density measurements by laser-induced fluorescence spectroscopy with two-photon excitation

The two-photon resonances of atomic hydrogen (lambda = 2 X 205.1 nm), atomi c nitrogen (lambda = 2 X 206.6 nm) and atomic oxygen (lambda = 2 X 225.6 nm ) are investigated together with two selected transitions in krypton (lambd a = 2 X 204.2 nm) and xenon (lambda = 2 X 225.5 mn). The natural lifetimes of the excited states, quenching coefficients for the most important collis ions partners, and the relevant ratios of the two-photon excitation cross s ections are measured. These data can be applied to provide a calibration fo r two-photon laser-induced fluorescence measurements based on comparisons w ith spectrally neighbouring noble gas resonances.