Check of OH rotational temperature using an interferometric method

Abstract

This paper presents an interferometric method used to check the rotational temperature of the OH free radical obtained using emission spectroscopy. The temperature is extracted from an interferogram via the phase shifting introduced by the refractive index of the studied medium. The refractive index is related to the temperature through the Gladstone–Dale equation and the ideal gas law.The method is tested on the laminar premixed flame of an oxy-acetylene burner and on the laminar plume of a dc argon plasma torch. The results obtained are compared with those obtained from the UV OH band at 306.357 nm (transition A2Σ, ν = 0 → X2Π, ν′ = 0) by emission spectroscopy using the Boltzmann plot method and using a method based on numerical simulated spectra with the amplitude ratios of groups of unresolved rotational lines.

Gas temperature and electron temperature measurements by emission spectroscopy for an atmospheric microplasma

“…Both emissions from N 2 and OH are suitable for gas temperature measurements. 17,30,[33][34][35][36][37][38][39] Unfortunately, in our measurements, nitrogen emission is often weak and seems to be affected by some other emission line; we suspect titanium emission lines which are present in the same spectral range and that might originate from etching of titanium atoms from the wire surface. [40][41][42] Therefore, the OH band has been chosen for gas temperature measurements.…”

“…Comparing synthetic spectra with experimental spectra the gas temperature could be computed by minimizing the error between the two spectra. The method has been de-scribed in detail and validated elsewhere 36,38 and relies on the assumption that rotational relaxation is much faster than vibrational and electronic transitions. The results are quite sensitive to the instrumental broadening parameter used for the computation of the synthetic spectra.…”

Nonequilibrium and effect of gas mixtures in an atmospheric microplasma

“…Although pure argon is injected in the capillary, nitrogen lines can be easily observed because the microplasma is generated in ambient air and, therefore, nitrogen easily mixes at the capillary exit. The method has been described in detail and validated elsewhere 10,11 and relies on the assumption that rotational relaxation is much faster than vibrational and electronic transitions. For the electron temperature, a technique described elsewhere 6,7 and based on a collisional-radiative model has been used.…”

Interferometer method using abel inversion to deduce a mapping of helium gas density and temperature

“…Raman scattering techniques sound, ultra‐sonic velocity electromagnetic wave probing, infrared spectra, absorption spectra, were all used to measure gas evolution in plasma. In general, these interferometry methods are interested in the measurement of the optical path in the medium, so this allows us to deduce the refractive index the density and the temperature from relationship between these parameters (Gladstone–Dale, Abel integral, ideal gas law).Some authors have studya method for determining the profile of density and temperature by boltzmann plot , and others have applied an advanced optical techniques which gives the temperature in a restricted localized area of the reacting flow such as Raman scattering , LIF , spectroscopy , Rayleigh scattering , and CARS . We found also some works, using a laser interferometric method, which measuring the complete spatial temperature distribution such as holographic interferometry , or interferometric finite fringe method based on determination of the refraction index distribution .…”