Accueil du site > Thèmes de recherche > Laser et Plasmas > English version > Characterization of laser-produced plasmas

Characterization of laser-produced plasmas

Contact : Jörg Hermann

The mechanisms involved into laser ablation are complex, in particular for irradiation with nanosecond pulses under ambient gas at atmospheric pressure. Thus, there does not exist any model that allows one to predict the plasma properties as functions of the material properties and the irradiation conditions. In particular, the plume expansion dynamics and the interaction of the ablated vapor with the surrounding ambient gas are not yet fully understood. Therefore, the processes of thermal and atomic diffusion, the role of chemical reactions, and the validity of local thermal equilibrium are in the focus of our interest.

For a better understanding of the processes, the plasma is investigated using fast plume imaging and time- and space-resolved optical emission spectroscopy. The plasma emission spectrum is analyzed by comparing it to theoretical spectrum computed for a plasma in local thermodynamic equilibrium.

Fig. 1. Plume expansion dynamics for material ablation with nanosecond UV laser pulses in low pressure argon.

Fig. 2. Spectral image recorded with an imagining spectrometer for an observation distance of 400 µm from the sample surface. We observe the spectral lines from the ablated vapor material in the core volume close to the plasma symmetry axis, whereas the emission from the argon gas is mainly located in the plume periphery.

Fig. 3. Emission spectra of a plasma produced by laser ablation of aluminum in argon (upper) and in air (lower). The spectrum recorded in argon is compared to spectral radiance of a uniform plasma in local thermodynamic equilibrium. The nonuniform plasma in air is described by two zones representing the hot core and the cold periphery of the plasma. The dips observed for the resonance lines Al I 308.21 et 309.27 nm are due to reabsorption by the cold peripheral volume.

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)

De Giacomo A., Hermann J., Laser-induced plasma emission : from atomic to molecular spectra, J. Phys. D : Appl. Phys. 50, 183002 1-17 (2017)

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)

Lagrange J.F., Hermann J., Wolfman J., Motret O., Time-resolved spatial distribution of plasma in the ablation of a Ba0.6Sr0.4TiO3 target by 25 ns KrF ultraviolet laser, J. Appl. Phys. 116, 133303 1-7 (2014)

Mercadier L., Hermann J., Grisolia C., Semerok A. Diagnostics of nonuniform plasmas for elemental analysis via laser-induced breakdown spectroscopy : demonstration on carbon-based materials, J. Anal. At. Spectrom. 28, 1446 – 1455 (2013)

Beldjilali S., Yip W.L., Hermann J., Baba-Hamed T., Belasri A., Investigation of plasmas produced by laser ablation using single and double pulses for food analysis demonstrated by probing potato skins, Anal. Bioanal. Chem. 400, 2173-2183 (2011)

Mercadier L., Hermann J., Grisolia C., Semerok A., Plume segregation observed in hydrogen and deuterium containing plasmas produced by laser ablation of carbon fiber tiles from a fusion reactor, Spectrochim. Acta Part B 65, 715-720 (2010)

Hermann J., Mercadier L., Mothe E., Socol G., Alloncle P., On the stoechiometry of mass transfer from solid to plasma during pulsed laser ablation of brass, Spectrochim. Acta Part B 65, 636-641 (2010)

Lagrange J. F., Hermann J., Wolfman J., Motret O., Dynamical plasma study during CaCu3Ti4O12 and Ba0.6Sr0.4TiO3 pulsed laser deposition by local thermodynamic equilibrium modelling, J. Phys. D : Appl. Phys. 43, 285202 1-6 (2010)