2D Raman imaging for vibrational and rotational temperature mapping in H2

Abstract

We showcase a Raman scattering diagnostic for 2D imaging of the rotational and vibrational temperatures of H₂. Applications include environments with vibrational-rotational non-equilibrium such as H₂-containing supersonic jets and plasma reactors. We image segments of the laser scattering spectrum, containing one or more Raman features, using an ICCD camera that is equipped with one of several bandpass filters. Knowing their transmission spectrum allows the construction of calibration curves that relate the relative intensities of the multi-spectral image to the rotational and vibrational temperatures. Additionally, the absolute intensity indicates the density of H₂. We illustrate the capability to independently measure rotational (300–3000 K, $\pm$150 K) and vibrational temperatures (1000–3000 K, $\pm$50 K). The technique is demonstrated on two different H₂ microwave plasmas and validated against conventional fitting of 0D and 1D Raman spectra.