A joint experimental and computational study is being conducted to investigate the effects of vibrational non-equilibrium on supersonic combustion, although the focus of this paper is on mixing between a supersonic jet and a subsonic coflow. A new facility has been constructed that consists of a Mach 1.5 turbulent jet issuing into an electrically heated coflow. In the preliminary experiments reported here, air is used in both the jet and the coflow. The degree of non-equilibrium in the jet shear layers is quantified by using high-spectral resolution timeaverage spontaneous Raman scattering. The Raman scattering is complemented with planar temperature imaging using Rayleigh scattering. Much of the current work is focused on the extent to which vibrational non-equilibrium can be assessed by using time-averaged Raman scattering in a turbulent flow with large-scale temperature fluctuations. The experimental work is supported by direct numerical simulation of related jet flows. Preliminary DNS of turbulent jets in coflow with imposed vibrational non-equilibrium shows that vibrational relaxation effects have a first-order effect on the jet temperature field and mixing physics. Nomenclature= specific heat at constant volume of species, α = vibrational energy = projected pixel dimension in physical plane = convective Mach number = incident laser power = Rayleigh scattered power = partition function − = translational-vibrational energy exchange , = reference temperature by which is defined for species, α = rotational temperature = translational temperature = vibrational temperature = passive scalar concentration = visual shear layer thickness  = characteristic vibrational temperature of an oscillator  = reduced mass of colliding pair 2  = vibrational relaxation timescale Ø = mass fraction of species, α = mixture fraction of species, α = collection solid angle ( ) = Rayleigh scattering cross-section

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