New Developments in the Physical Chemistry of Shock Compression

Dlott, Dana D.

doi:10.1146/annurev.physchem.012809.103514

Cited by 78 publications

(57 citation statements)

References 141 publications

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“…An example calculation shows that for a pump fluence of 18.9 mJ/ cm 2 , a strain of 1:5 Â 10 À3 , or a pressure of 7 kbar, builds up in less than a picosecond for a 20 micrometer thick sapphire sample. A possible example of application is the study of material deformation under ultrafast shock compression [55].…”

Section: Ultrafast Shock Waves -Burgers Equationmentioning

confidence: 99%

Nonlinear ultrafast acoustics at the nano scale

2015

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Pulsed femtosecond lasers can generate acoustic pulses propagating in solids while displaying either diffraction, attenuation, nonlinearity and/or dispersion. When acoustic attenuation and diffraction are negligible, shock waves or solitons can form during propagation. Both wave types are phonon wavepackets with characteristic length scales as short as a few nanometer. Hence, they are well suited for acoustic characterization and manipulation of materials on both ultrafast and ultrashort scales. This work presents an overview of nonlinear ultrasonics since its first experimental demonstration at the beginning of this century to the more recent developments. We start by reviewing the main properties of nonlinear ultrafast acoustic propagation based on the underlying equations. Then we show various results obtained by different groups around the world with an emphasis on recent work. Current issues and directions of future research are discussed.

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Section: Ultrafast Shock Waves -Burgers Equationmentioning

confidence: 99%

Nonlinear ultrafast acoustics at the nano scale

2015

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“…III, were performed for spatially resolved regions containing contiguous molecular layers (e.g., ignoring minus signs, layers 1-2, 1-10, 61-80, etc.). Immediately behind the shock front the five two-layer-thick regions (again, ignoring minus signs) 1-2, 3-4, 5-6, 7-8, and 9-10 were used to define a ten-layer-thick one (1)(2)(3)(4)(5)(6)(7)(8)(9)(10). Throughout the analysis we considered only layers −1 to −220 behind the shock front and layers +1 to +20 ahead of the shock front.…”

Section: Of Ref 3 For An Illustration Of the Simulation Cellmentioning

confidence: 99%

“…[1][2][3][4] To make full use of shocks as an experimental technique for rapidly adding energy to solids or liquids, it is important that we come to understand the fundamental behavior of shocks in complicated anisotropic materials and at interfaces. [5][6][7][8] The large anisotropic strains and high strain rates imposed by shock wave passage through a crystal result in molecules containing relatively large amounts of energy that is, in general, non-thermally distributed immediately behind the shock front. Phonon and molecular modes that are close to mechanical resonances with the shock wave are preferentially excited, after which redistribution of the shock excitation energy to the remaining modes of the system occurs; this mechanism is widely accepted 9,10 and has come to be known as vibrational multi-phonon up-pumping.…”

Section: Introductionmentioning

confidence: 99%

Post-shock relaxation in crystalline nitromethane

Rivera‐Rivera

Sewell

Thompson

2013

The Journal of Chemical Physics

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Molecular dynamics simulations of shocked (100)-oriented crystalline nitromethane were carried out to determine the rates of relaxation behind the shock wave. The forces were described by the fully flexible non-reactive Sorescu-Rice-Thompson force field [D. C. Sorescu, B. M. Rice, and D. L. Thompson, J. Phys. Chem. B 104, 8406 (2000)]. The time scales for local and overall thermal equilibration in the shocked crystal were determined. The molecular center-of-mass and atomic kinetic energy distributions rapidly reach substantially different local temperatures. Several picoseconds are required for the two distributions to converge, corresponding to establishment of thermal equilibrium in the shocked crystal. The decrease of the molecular center-of-mass temperature and the increase of the atomic temperature behind the shock front exhibit essentially exponential dependence on time. Analysis of covalent bond distance distributions ahead of, immediately behind, and well behind the shock front showed that the effective bond stretching potentials are essentially harmonic. Effective force constants for the C-N, C-H, and N-O bonds immediately behind the shock front are larger by factors of 1.6, 2.5, and 2.0, respectively, than in the unshocked crystal; and by factors of 1.2, 2.2, and 1.7, respectively, compared to material sufficiently far behind the shock front to be essentially at thermal equilibrium.

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“…13,15 The time resolution of gas gun experiments of this type is typically several ns. 16,17 a) Author to whom correspondence should be addressed. Electronic mail:…”

Section: Introductionmentioning

confidence: 99%

Laser-driven flyer plates for shock compression science: Launch and target impact probed by photon Doppler velocimetry

Curtis

Банишев

Shaw

et al. 2014

Review of Scientific Instruments

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We investigated the launch and target impact of laser-driven Al flyer plates using photon Doppler velocimetry (PDV). We studied different flyer designs launched by laser pulses of different energies, pulse durations and beam diameters, that produced km s(-1) impacts with transparent target materials. Laser-launching Al flyers 25-100 μm thick cemented to glass substrates is usually thought to involve laser vaporization of a portion of the flyer, which creates many difficulties associated with loss of integrity and heating of the flyer material. However, in the system used here, the launch mechanism was surprising and unexpected: it involved optical damage at the glass/cement/flyer interface, with very little laser light reaching the flyer itself. In fact the flyers launched in this manner behaved almost identically to multilayer flyers that were optically shielded from the laser pulses and insulated from heat generated by the pulses. Launching flyers with nanosecond laser pulses creates undesirable reverberating shocks in the flyer. In some cases, with 10 ns launch pulses, the thickest flyers were observed to lose integrity. But with stretched 20 ns pulses, we showed that the reverberations damped out prior to impact with targets, and that the flyers maintained their integrity during flight. Flyer impacts with salt, glass, fused silica, and acrylic polymer were studied by PDV, and the durations of fully supported shocks in those media were determined, and could be varied from 5 to 23 ns.

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New Developments in the Physical Chemistry of Shock Compression

Cited by 78 publications

References 141 publications

Nonlinear ultrafast acoustics at the nano scale

Nonlinear ultrafast acoustics at the nano scale

Post-shock relaxation in crystalline nitromethane

Laser-driven flyer plates for shock compression science: Launch and target impact probed by photon Doppler velocimetry

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