Abstract

Molecular nitrogen, N₂, is one of the most important molecules in combustion and environmental diagnostics since it constitutes the major species of our atmosphere. For temperature and concentration measurements N₂ CARS has been developed into a highly robust and accurate tool. There are environments where N₂ concentrations are too low for CARS to be applicable. In this case excitation schemes can be used which have been developed to allow direct access to electronic resonances of N₂ via multi-photon transitions [1]. Almost all detection schemes of these techniques employ further resonant multi-photon steps to create N₂⁺ ions and the resulting signal electrons are collected by electrodes (resonance enhanced multi-photon ionisation - REMPI) [2,3].

© 1996 Optical Society of America