Optical spectroscopy investigation of N₂–CH₄plasma jets simulating Titan atmospheric entry conditions

Abstract

Planetary probes penetrating at supersonic speed into high atmosphere require the development of composite materials for thermal protection of the surface exposed to a high enthalpy flux. Rarefied arc plasmas can be used to simulate the atmospheric re-entry plasmas. The aim of this paper is to describe the latest results of optical emission measurements of the CH (A-X) system, the CN violet (B-X) bands and the NH (A-X) electronic transitions in a N 2 -CH 4 plasma source (Titan's atmosphere) and in a gas mixture of Ar-CH 4 . In order to deduce the plasma parameters, such as rotational and vibrational temperatures, of these molecular species in the plasma environment, numerical simulation codes have been implemented. In this context, rotational temperatures near 7000 K for CN and 3500 K to 2800 K for the hydrides NH and CH, respectively, are observed. The vibrational temperature of the CH molecule is around 3800 K while those of the CN and NH molecules are 9500 K and 7900 K, respectively.

Uncertainty Analysis of Radiative Heating for Multiple Planetary Entry Cases (Invited)

“…Emission from NH molecule excited states have also been identified as a potential source of radiation. 54 Brandis et al 55 showed that the primary NH transition does not contribute significantly to the radiation as is, therefore, ignored in the present study. The effect of atomic line emission and photoionization from C and N atoms was also investigated, but was found to contribute less than 1% to the total radiative heat flux and are not considered throughout this study…”

The Diffusion of Low-Energy Methyl Group on ITO Film Surface and Its Impact on Optical-Electrical Properties

“…The detailed description was discussed in our previous publication [18,19]. Based on the plasma theory and the methane dehydrogenation process in plasma, methyl cation (${\mathrm{boldCH}}_3^{+}$), methylene cation (${\mathrm{boldCH}}_2^{+}$), and methine cation (${\mathrm{boldCH}}_{}^{+}$) were formed in the ion source [20,21,22,23]. Therefore, the methyl group beam contained the above three kinds of cation.…”

Dissociative Excitation of Nitromethane Induced by Electron Impact in the Ultraviolet – Visible Spectrum

“…Figure 3. Most prominent molecular bands and Balmer lines in nitromethane emission spectrum obtained at 50 eV and 0.4 nm optical resolution identified according to [15] and [19][20][21][22][23]. The spectrum has been corrected for the wavelength dependent sensitivity of the apparatus.…”