Optical and X-ray emission spectroscopy of high-power laser-induced dielectric breakdown in molecular gases and their mixtures

Large-scale plasma was created in molecular gases (CO, CO2, N-2, H2O) and their mixtures by high-power laser-induced dielectric breakdown (LIDB). Compositions of the mixtures used are those suggested for the early earth's atmosphere of neutral and/or mildly reducing character. Time-integrated optical spectra emitted from the laser spark have been measured and analyzed. The spectra of the plasma generated in the CO-containing mixtures are dominated by emission of both C-2 and CN radicals. A vibrational temperature of similar to 10(4) K was determined according to an intensity distribution in a vibronic structure of the CN (B-2 Sigma(+)(u)-X-2 Sigma(+)(g)) violet band. For comparison, the NH3-CH4-H-2-H2O mixture has been irradiated as a model of the strongly reducing version of the early earth's atmosphere. In this mixture, excited CN seems to be significantly less abundant than C2. The LIDB experiments were in the molecular gases carried out not only in the static cell but also using a large, double stream pulse jet (gas puff target) placed in the vacuum interaction chamber. The obtained soft X-ray emission spectra indicate the presence of highly charged atomic ions in the hot core of high-power laser sparks

Laser diode photoacoustic spectroscopy near 2.3 µm

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Room-temperature diode laser photoacoustic spectroscopy near 2.3 µm

International audienceWe describe results obtained with a new type of GaSb-based semiconductor distributed feedback multiple quantum well lasers operating in continuous-wave mode at room temperature and above. The lasers show good tunability both by the excitation current and the temperature from -1 °C to +60°C (4170 to 4360 cm-1). They operate in a high-power (more than 1 mW) single-mode regime and can be tuned without hopping in the methane and ammonia absorption spectral range of up to 15 cm-1. Application to photoacoustic detection is also described. Potential use lies in the areas of analytical chemistry of gases and in atmospheric pollution research

Laser diode photoacoustic spectroscopy near 2.3 µm

International audienc