Two-zone elastic-plastic single shock waves in solids

By decoupling time and length scales in moving window molecular dynamics shock-wave simulations, a new regime of shock-wave propagation is uncovered characterized by a two-zone elastic-plastic shock-wave structure consisting of a leading elastic front followed by a plastic front, both moving with the same average speed and having a fixed net thickness that can extend to microns. The material in the elastic zone is in a metastable state that supports a pressure that can substantially exceed the critical pressure characteristic of the onset of the well-known split-elastic-plastic, two-wave propagation. The two-zone elastic-plastic wave is a general phenomenon observed in simulations of a broad class of crystalline materials and is within the reach of current experimental techniques.     

Acoustic probing of two-temperature relaxation initiated by action of ultrashort laser pulse

Ultrashort laser pulse transfers metal into a two-temperature warm dense matter state and triggers a chain of hydrodynamic and kinetic processes—melting, expansion, stretching, creation of tensile stress and transition into metastable state. We study the response of aluminum film deposited on a glass substrate to irradiation by a pump laser pulse transmitted through glass. Several films with thicknesses from 350 to 1200 nm have been investigated. The smallest thickness is of the order of the heating depth d _T∼100 nm in Al. The d _T-layer and the free rear side of the film are coupled through pressure waves propagating between them. Therefore, the processes within d _T-layer affects the time dependent displacement Δ x _rear(t) of the rear surface. We compare simulated and experimental dependencies Δ x _rear(t) obtained by the pump–probe technique. It allows us to define a thickness of molten Al layer and explore the two-temperature processes occurring inside the heated layer.     

Melting of Titanium by a Shock Wave Generated by an Intense Femtosecond Laser Pulse

JETP Letters - Laser shock peening with ultrashort laser pulses has been studied by hydrodynamic and atomistic simulations, as well as experimentally. It has been shown that, in contrast to...     

High-Energy-Density Physics and Laser Technologies

Journal of Experimental and Theoretical Physics - This paper is devoted to the jubilee of I.M. Khalatnikov, the founder and the first director of the Landau Institute for Theoretical Physics of the...     

Laser Acoustic Probing of Two‐Temperature Zone Created by Femtosecond Pulse

We combine theoretical and experimental methods to study the processes induced by fast laser heating of metal foils. These processes reveal themselves through motion of frontal (irradiated) and rear‐side foil boundaries. The irradiated targets are 0.3‐2 micron thick aluminum foils deposited on much thicker (150 microns) glass plate. The instant boundary positions is measured by pump‐probe technique having ∼40‐150 fs time and ∼1 nm spatial resolutions. Ultrashort laser pulse transforms a frontal surface layer with thickness d_T into two‐temperature (T_e ≫ T_i) warm dense matter state. Its quantitative characteristics including its thickness are defined by poorly known coefficients of electron‐ion energy exchange α and electron heat conductivity κ. Fast laser heating rises pressure in the d_T‐layer and therefore produce acoustic waves. Propagation and reflection from the frontal and rear boundaries of these waves causes the displacement Δx (t) of boundary positions. Pressure wave profiles, and hence functions Δx (t), depend on thickness d_T. This is why the experimental detection of Δx (t) opens a way to accurate evaluation of the coefficients α and κ (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Erratum to: Several Articles in JETP Letters

JETP Letters - An Erratum to this paper has been published: https://doi.org/10.1134/S0021364022350016     

Condensation of laser‐produced gold plasma during expansion and cooling in a water environment

Physical processes involved in laser ablation in liquid (LAL) are studied using a gold target irradiated through transparent water. During and after irradiation, the heated material from the surface of a target produces a plume that expands into liquid‐forming nanoparticles (NPs). The LAL method of NP production is ecologically much cleaner than others. A better understanding of the processes associated with complicated hydrodynamic phenomena leading to LAL is important for controlled manufacturing. We consider laser pulses with different durations τ_L covering fifth orders of magnitudes ranging from 0.1 ps to 0.5 ns and large absorbed fluences F_abs near optical breakdown of liquid. It is shown that the trajectory of the contact boundary with liquid at the middle and late stages after passing the maximum intensity of the longest pulse is rather similar for very different pulse durations if energies F_abs are comparable. We trace how hot (in a few eV range) dense gold plasma expands, cools down, intersects a saturation curve, and condenses into NPs appearing first inside the water‐gold diffusively mixed intermediate layer where gold vapour has the lowest temperature. Later, the pressure around the gold‐water contact drops down below the critical pressure for water. As a result, the nanoparticles find themselves in gaseous water bubble where density of water gradually decreases to 10^?4 ? 10^?5  g/cm³ at maximum bubble expansion.     

Redistribution of a material at femtosecond laser ablation of a thin silver film

Energy-dispersive X-ray microspectroscopy is used for the first time to quantitatively study the spatial displacement of the material of a 100-nm silver film irradiated by a single femtosecond laser pulse focused on a small spot in the diffraction limit. The silver mass distribution over radial cross sections is determined and matter balance is analyzed for the resulting radially symmetric submicron structures of a microcone with a nanospike with various heights and a through hole. Hydrodynamic processes and phase transitions inducing the melting of the film, motion of the melt, and its recrystallization within a focal spot are studied.     

Physical Processes Accompanying Laser Ablation in Liquid

JETP Letters - Ablation in liquid is numerically simulated with molecular dynamics and hydrodynamics codes. Laser radiation passes through a transparent liquid, illuminates a metal target, and is...