Coherent Anti-Stokes Raman Spectroscopy of Gases

Coherent anti-Stokes Raman spectroscopy, or CARS as it has come to be known, is a relatively new spectroscopic technique which has gained considerable interest over the past few years because of its potential use as a powerful analytical tool and because of its unique and curious properties [1–98], Several review articles on the subject have been written recently [4, 30, 33, 35, 49, 67, 72, 90]. Some papers have attempted to describe the theoretical background [30, 33] and others have surveyed the entire subject matter [4, 35, 49, 67, 72, 90]. In this report we will review only CARS spectroscopy of gases. However, because of recent progress it might be well to at least reference some new results [18–21, 42, 47, 66] in resonance and “normal” CARS of biological and fluorescent materials in dilute solution (as low as ∼ 10−7 M). Moreover, since the emphasis of this paper is on applications, we will not attempt to derive the theory or the principles behind CARS but merely describe the results.