Analysis of the plasma expansion dynamics by optical time-of-flight measurements

Theoretical modelling of phenomena in the pulsed-laser deposition process: Application to Ti targets ablation in low-pressure N2

“…53 In addition, Optical emission spectroscopy ͑OES͒ studies indicated an ambipolar diffusion, which may be responsible for an acceleration of the ions up to hyperthermal velocities. [50][51][52] We note that the experimental investigation of plasma parameters is a quite difficult task in the initial phase of the expansion. In our opinion, this might be an effect of the high optical thickness of the spectral lines emitted from the initially very dense plasma.…”

“…We emphasize that highly energetic plasma particles of energies as high as 100-150 eV were demonstrated experimentally. [50][51][52] The formation of such particles can be accounted for by mecha- FIG. 7.…”

Ablation de ZnO par laser UV (193 nm) : nano-agrégats en phase gazeuse

“…Pendant les premières 50 nanosecondes après l'impulsion laser, le spectre est non structuré et correspond à superposition de la luminescence des nano-agregats avec un continuum dans une région spectrale comprise entre 2, 3 et 3, 8 eV. Ces spectres de continuum correspondent à l'émission observée pendant les stades initiaux de formation du plasma d'ablation (processus de Bremsstrahlung) [8]. Des raies fines d'émission des atomes neutres de zinc apparaissent 50 ns après l'impulsion du laser d'excitation.…”

Expansion Dynamics of Carbon Cluster Inos (Cn+, n=1-24)Produced by Laser Ablation of a Graphita Target

“…When the transient electric field in the plume plays a dominant role in the acceleration of ions, the velocities of ions are proportional to 1/ . 11 However, the reason why the mean kinetic energy of C + ions is smaller and that of C 3 + ions is larger than those of other ions is not clear yet. Since the laser-produced carbon plume is a complicated system, the expansion of each ion is expected to be influenced by reactive and nonreactive scatterings in the plume as well as the local electric field.…”

“…The TOF distributions of C 11 + and C 18 + ions are quite broadened since they are produced mainly by fragmentation of larger clusters and their scattering cross sections in the plume are relatively large. In particular, C 11 + ions show a clear bimodal distribution, which indicates collision-induced dissociation of larger cluster ions. Such bimodal distribution is not clearly observed for other ions presumably because the velocity distributions are narrow or the signal-to-noise ratios are low.…”