CARS measurements in an internal combustion engine

The first reported coherent anti-Stokes Raman scattering (CARS) experiments within the cylinder of a firing internal combustion engine are described. The feasibility of making noninvasive temperature and species measurements, with good spatial and temporal resolution, both before and after ignition has been demonstrated. Temperatures have been derived from the shape of the Q-branch vibrational spectrum of nitrogen since it is present as a major species and does not take part in combustion. Methods of overcoming such problems as were encountered are discussed.