The methane Raman spectrum from 1200 to 5500 cm−1: A first step toward temperature diagnostic using methane as a probe molecule in combustion systems

We present a study of the spontaneous Raman spectra of 12CH4 from 1200 to 5500 cm−1 at various temperatures. This study is of interest from a fundamental as well as from a practical point of view with regards to the temperature diagnostic in hydrocarbon combustion. The present investigation shows that the spontaneous 12CH4 Raman spectra are very sensitive to temperature and that the complexity of methane spectra is not an obstacle to use methane as a probe molecule in laser-diagnostic techniques. Our study consists in determining the polarisability parameters of methane 12CH4, unknown at the present time, from spontaneous Raman spectra recorded at pressure less than one atmosphere to minimize the problem of line-mixing. This diagnostic method technique based on spontaneous Raman spectroscopy may be applied to temperature measurements in a uni-element rocket combustion chamber using methane-oxygen propellants.