The discharge equilibrium and the F-atom production kinetics in a phototriggered HF laser using gas mixtures containing Ne and with hydrogen or ethane have been investigated. Coupled experimental and theoretical studies have been carried out, through a 0D discharge modelling and measurements of the current, of the voltage and of the extracted laser energy, together with emission spectroscopy on F 3p excited states. A quantitative comparison of the total F-atom density produced in mixtures of with or is performed and the results are compared with the discharge pumped HF laser performance achieved with these molecules. An overall validation of the model has been obtained, both for the energy transfer to the active media and for the kinetics of F and its excited states. It is shown that the transmitted energy and electrical charge, as well as the discharge electric field, weakly depend on the type and on the concentration of the RH molecule, or , in the gas mixtures. Moreover, the F-atom production depends very slightly on the nature of RH. Therefore the fact that the laser performance achieved with hydrogen is lower than the performance achieved with ethane is not due to differences in the energy transfer and in the F-atom production kinetics in mixtures of with or .

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X-ray photo-triggered discharges have been used to energetize NeJSFflI2 and Ne/SF6/C2H gas mixtures. For a discharge volume of3 12 cm3 an output energy as high as 3 .0 J has been obtained in the ethane mixture, while the best laser performance achieved in the hydrogen mixture is only 1.8 J. The physical reasons which could explain these differences, i.e. different kinetic pathways leading to the formation ofthe HF molecule, or the onset ofdischarge instabilities, have been investigated. It is shown, experimentally and theoretically, that the production of atomic fluorine weakly depends on the gas mixture type. A time resolved imagery ofthe interelectrodes space emphasised that the Ne/SF6IH2 active medium degenerates into a spatially inhomogeneous plasma, whereas a very stable homogeneous discharge is obtained in the Ne/SF6/C2H mixture. As a result the onset ofa discharge instability is responsible for the laser emission collapse at low hydrogen partial pressure and high initial applied electric field values.

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