This work is devoted to the experimental investigation of the high temperature kinetics and spectroscopy of astrophysical gases. A versatile and existing High Enthalpy Source (HES) coupled with a flow tube and with a Pulsed-Laser-Photolysis-Laser Induced Fluorescence (PLP-LIF) system has been adapted to measure the kinetics of key high temperature neutral-radical reactions of interest for the chemistry of circumstellar envelopes of carbon rich red giant stars characterized by surface layer temperatures between 1000K and 4000K. The HES can achieve temperatures up to 1800 K, it is based on a heated graphite rod, whose open porosity provides a huge exchange surface. The first part of this thesis describes the design and the characterization of this new prototype, in particular with the help of computational flow dynamic simulations. The second part deals with the kinetic studies of the reaction of the cyano (CN) radical with propane (C3H8), propene (C3H6), propadiene (C3H4), 1,3-butadiene (1,3-C4H6), 1-butyne (1-C4H6) and ammoniac (NH3) over a temperature range extending from 300 to 1200 K. The temperature dependent rate constants have been fitted to a modified Arrhenius expression of the form. The majority of the reactions studied are rapid, with rate constants greater than 10-10 cm3.molecule-1.s-1. The last part of the thesis is devoted to the high temperature emission spectroscopy of methane and acetylene whose infrared opacity at high temperature is required to model the thermal structure of carbon-rich evolved stars. The infrared emission is recorded at 3 mirons for methane and 13,7 microns for acetylene at Doppler resolution with a high resolution Fourier transform interferometer (Bruker IFS 125HR), for temperatures ranging in the 1000-1750 K interval. A radiative transfer model has been developed to quantify the self-absorption effect on the line-by-line absorption cross sections extracted from the recorded spectra. A "2 T" method has been used to access to the energy value and rotational assignment of the angular momentum J of the lower state of a given transition. Some difficulties relative to the application of this method to our emission spectra are discussed.
