36 research outputs found
Dynamics of the plume formation and parameters of the ejected clusters in short-pulse laser ablation
Pulsed laser ablation and incubation of nickel, iron and tungsten in liquids and air
Incubation effects in the nanosecond laser ablation of metals exhibit a strong dependence on the thermal and mechanical properties of both the target material and the background gas or liquid. The incubation in air is controlled mainly by thermal properties such as the heat of vaporization. In liquid, the correlation of the incubation and the ultimate tensile stress of the metals suggests that incubation may be related to the mechanical impact on the solid material by the cavitation bubble collapse, causing accumulation of voids and cracks in the subsurface region of the ablation craters. At high ultimate tensile stress, however, the low sensitivity to the environment suggests that the mechanical impact is likely to play a negligible role in the incubation. Finally, the correlation between the incubation and the carbon content of alcoholic liquids may be explained by an absorptivity increase of the cavity surfaces due to carbonaceous deposits generated by laser-induced pyrolysis, or by the mechanical impact of long-living bubbles at higher dynamic viscosity of liquids
Silicon clusters produced by femtosecond laser ablation: Non-thermal emission and gas-phase condensation
Neutral silicon clusters Si_n (up to n = 7) and their cations Si_n+ (up to n
= 10) have been produced by femtosecond laser ablation of bulk silicon in
vacuum and investigated using time-of-flight mass spectrometry. Two populations
of the Si_n+ clusters with different velocity and abundance distributions in
the ablation plume have been clearly distinguished. Possible mechanisms of
cluster formation (Coulomb explosion, gas-phase condensation, phase explosion)
are discussed
Spallative ablation of dielectrics by X-ray laser
Short laser pulse in wide range of wavelengths, from infrared to X-ray,
disturbs electron-ion equilibrium and rises pressure in a heated layer. The
case where pulse duration is shorter than acoustic relaxation time
is considered in the paper. It is shown that this short pulse may cause
thermomechanical phenomena such as spallative ablation regardless to
wavelength. While the physics of electron-ion relaxation on wavelength and
various electron spectra of substances: there are spectra with an energy gap in
semiconductors and dielectrics opposed to gapless continuous spectra in metals.
The paper describes entire sequence of thermomechanical processes from
expansion, nucleation, foaming, and nanostructuring to spallation with
particular attention to spallation by X-ray pulse
Mechanisms of laser ablation from molecular dynamics simulations: dependence on the initial temperature and pulse duration
Mechanisms of laser ablation from molecular dynamics simulations: dependence on the initial temperature and pulse duration
Évolution temporelle des agrégats créés par impulsions laser courtes : évaporation et condensation
L'étude numérique du comportement d'un
panache gazeux et d'un nano-agrégat créés lors l'ablation laser
par impulsions courtes est étudiée par la méthode de dynamique
moléculaire. Lors de l'évolution d'une nanoparticule, deux
phénomènes coexistent : l'agglomération (ou agrégation) et
l'évaporation. La température seuil de la nanoparticule à partir
de laquelle l'évaporation prédomine est ainsi déterminée. La
présence du panache gazeux modifie ce comportement. D'autre part la
condensation de ce gaz est un paramètre non négligeable dans la
poursuite de cette étude