Laser-based spectroscopic technique for fast and reliable measurements of lifetimes of atomic metastable states in combustive situations

Abstract

A technique for a fast and reliable determination of the lifetime of atomic metastable states in combustive situations, based on the laser-enhanced ionization technique, is developed. The typical time required for a determination of the lifetime of an atomic metastable state in a given local position in a combustive situation ranges from some seconds to a minute (depending on the signal-to-noise ratio). The lifetime of the lowest metastable state in Au in an acetylene-air flame, which is used as the pilot metastable state in this paper, was found to vary over one order of magnitude (between 600 ns and 8.8 micros), depending on the local stoichiometric conditions in the probe volume (which, in turn, is a function of the probing position and the fuel-air ratio fed to the flame). It is demonstrated that the probing of the lifetime of atomic metastable states by this new technique can thus be used as a sensitive tool for mapping local stoichiometric conditions in a flame.