Shock temperature and reflectivity of precompressed H ₂ O up to 350 GPa: Approaching the interior of planets

Abstract

Using a combination of static precompression and laser-driven shock compression, shock temperature and reflectivity of H 2 O have been measured up to 350 GPa and 2.1×10 4 K. Here, two calibration standards were applied to enhance temperature measurement reliability. Additionally, in temperature calculations, the discrepancy in reflectivity between active probe beam wavelength and self-emission wavelength has been taken into account to improve the data's precision. Precompressed water's temperature-pressure data are in very good agreement with our quantum molecular dynamics model, suggesting a superionic conductor of H 2 O in the icy planets' deep interior. A sluggish slope gradually approaching Dulong-Petit limit at high temperature was found at a specific heat capacity. Also, high reflectivity and conductivity were observed at the same state. By analyzing the temperature-pressure diagram, reflectivity, conductivity and specific heat comprehensively at conditions simulating the interior of planets in this work, we found that as the pressure rises, a change in ionization appears; it is supposedly attributed to energetics of bond-breaking in the H 2 O as it transforms from a bonded molecular fluid to an ionic state. Such molecular dissociation in H 2 O is associated with the conducting transition because the dissociated hydrogen atoms contribute to electrical properties.

Calibration and verification of streaked optical pyrometer system used for laser-induced shock experiments

“…However, in shock-wave experiments, , which gives . Since , where is the difference in reflectivity between the SOP channel and the VISAR probe beam, it can be regarded as a constant in a certain state [10, 11] . is the reflectivity of base material, while and are the camera counts of the shocked material and base material, respectively.…”

“…Shock temperature measurements are among the important means to examine and test the theoretical EOS model under extreme conditions. High-power lasers have been increasingly used as drivers for shock-wave experiments, and can produce extremely high pressures [5][6][7][8][9][10][11] .…”

High-pressure electrides: From design to synthesis

“…High pressure is an effective way to discover or modify materials with intriguing physical and chemical properties. [38][39][40][41][42] Extensive theoretical and experimental ef-forts greatly enrich the variety of high-pressure electrides (HPEs). For example, elemental electrides of Li, [43][44][45] Na, [26,46] K, [45,47] Cs, [48] Al, [49] and C; [50] and new compounds of Na 2 He, [51] Ca 5 C 2 , [52] Li 6 P, [18] Na 2 K, [53] and Ti 2 O.…”