2D Raman imaging for vibrational and rotational temperature mapping in H<inf>2</inf>

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, ±150 K) and vibrational temperatures (1000–3000 K, ±50 K). The technique is demonstrated on two different H2 microwave plasmas and validated against conventional fitting of 0D and 1D Raman spectra.