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Laser plasma for investigations of atomic or molecular structure

Contact : Jörg Hermann

According to their small size and high brilliance, plasmas produced by pulsed lasers are ideal emission sources for the study of the atomic or molecular structure. Any kind of atomic or molecular species can be investigated, as long as their radiative transitions can be observed by the detection system. If material ablation is produced with UV nanosecond laser pulses under argon atmosphere, the plume is characterized by almost uniform spatial distributions of temperature and density. The uniform character is explored in the measurements of spectroscopic data such as Stark broadening parameters and transitions probabilities of spectral lines. Many data are missing or are tabulated with low accuracy in the spectroscopic databases, in particular for transitions of species that belong to elements of large atomic mass.

Fig. 4. Saha-Boltzmann plot for temperature measurements of the plasma produced by laser ablation of aluminum in argon. We deduce a temperature decrease from 15000 to 8000 K during the time from 350 to 5000 ns.

Fig. 5. Spectral lines of aluminum with transition probabilities Aul that are not tabulated in the NIST database. The Aul –values deduced from the simulations differ by a factor of two from the calculated values tabulated in the Kurucz database.

Publications :

Hermann J., Grojo D., Axente E., Gerhard C., Burger M., Craciun V., Ideal radiation source for plasma spectroscopy generated by laser ablation, Phys. Rev. E 96, 053210 1-6 (2017)

Burger M., Hermann J., Stark broadening measurements in plasmas produced by laser ablation of hydrogen containing compounds, Spectrochim. Acta Part B 122, 118–126 (2016)

Hermann J., Lorusso A., Perrone A., Strafella F., Dutouquet C., Torralba B., Simulation of emission spectra from nonuniform reactive laser-induced plasmas, Phys. Rev. E 92, 053103 1-15 (2015)

Hermann J., Gerhard C., Axente E., Dutouquet C., Comparative investigation of laser ablation plumes in air and argon by analysis of spectral line shapes : Insights on calibration-free laser-induced breakdown spectroscopy, Spectrochim. Acta Part B 100, 189-196 (2014)

Cirisan M., Cvejic M., Gavrilovic M.R., Jovicevic S., Konjevic N., Hermann J., Stark broadening of Al II lines in a laser-induced plasma, J. Quant. Spectrosc. Radiat. Transfer. 133, 652-662 (2014)