Flame Temperatures from Vibrational Raman Scattering

Abstract

Raman scattering signatures are functionally dependent upon temperature, and are therefore useful as diagnostic probes. Various Raman scattering techniques for the measurement of temperature are outlined here. Those methods based upon rotational molecular structure are then briefly discussed in order to compare and contrast them with the ones based upon vibrational structure. For flame gases, the elevated temperatures and the multicomponent, variable composition make the vibrational scattering techniques appear to be more useful than those based upon pure rotational scattering. Temperature measurements based upon vibrational Raman scattering are described next, with an emphasis on the vibrational techniques developed in this laboratory. These techniques are based upon the spectral structure of the fundamental Stokes vibrational band series, which consists of the ground state band (initial → final molecular vibrational levels: v = 0 → v = 1) and the upper state or “hot” bands (1 → 2, 2 → 3, etc.).