Laboratory for Plasma Physics (LPP) Ecole polytechnique

Supervisor: Svetlana Starikovskaia (www.lpp.fr)

Spectroscopy, as a diagnostic technique, represents a broad class of methods based on the internal structure of atoms and molecules. In physics and chemistry, atoms and molecules in the object of study are subjected to changes which lead to modification of their absorption/emission spectra. Registration of the emission in UV-visible-IR range gives detailed information about the properties of the object. More comprehensive laser methods, such as laser induced fluorescence (LIF), two-photon absorption laser induced fluorescence (TALIF) use a selective laser excitation of atoms/molecules with subsequent registration of the spectra of fluorescence.

Low-temperature nonequilibrium plasma of gas discharges is naturally connected with spectroscopy: emission spectra, observed in gas discharges, are due to excitation of internal states of atoms and molecules. The examples of excitation of internal levels of atoms/molecules with the subsequent emission in UV-visible range of the spectrum can be found in nature. They are, for example, aurora borealis, high-altitude lightning (so-called blue jets and red sprites) and so on.

During the Project, the students will make a review of spectroscopy techniques used to measure gas parameters in different domains (plasma, combustion, chemistry) and will apply their knowledge to measure, by emission spectroscopy, a temperature of gas in discharge in synthetic air (N2:O2=4:1 mixture). Students will measure, using a spectrometer and ICCD camera, the emission spectra, will identify the transitions, will learn how to link the spectra with internal parameters of the gas and will write a code to treat the experimental data.

Fig.1 Laboratory plasma: glow discharge in supersonic air flow

Fig.2 Plasma in nature: scheme of high-altitude discharges