| 1 | Observation of a highly conductive warm dense state of water with ultrafast pump–probe freeelectron-laser measurements显示文摘The electrical conductivity of water under extreme temperatures and densities plays a central role in modeling planetary magnetic fields.Experimental data are vital to test theories of high-energy-densitywater and assess the possible development and presence of extraterrestrial life.These states are also important in biology and chemistry studies when specimens in water are confined and excited using ultrafast optical or free-electron lasers(FELs).Here we utilize femtosecond optical lasers to measure the transient reflection and transmission of ultrathin water sheet samples uniformly heated by a 13.6 nm FEL approaching a highly conducting state at electron temperatures exceeding 20000 K.The experiment probes the trajectory ofwater through the high-energy-density phase space and provides insights into changes in the index of refraction,charge carrier densities,andACelectrical conductivity at optical frequencies.At excitation energy densities exceeding 10MJ/kg,the index of refraction falls to n0.7,and the thermally excited free-carrier density reaches ne531027 m−3,which is over an order of magnitude higher than that of the electron carriers produced by direct photoionization.Significant specular reflection is observed owing to critical electron density shielding of electromagnetic waves.Themeasured optical conductivity reaches 23104 S/m,a value that is one to two orders of magnitude lower than those of simplemetals in a liquid state.At electron temperatures below 15000 K,the experimental results agreewell with the theoretical calculations using density-functional theory/molecular-dynamics simulations.With increasing temperature,the electron density increases and the system approaches a Fermi distribution.In this regime,the conductivities agree better with predictions from the Ziman theory of liquid metals. | Z.Chen X.Na C.B.Curry S.Liang M.French A.Descamps D.P.DePonte J.D.Koralek J.B.Kim S.Lebovitz M.Nakatsutsumi B.K.Ofori-Okai R.Redmer C.Roedel M.Schörner S.Skruszewicz P.Sperling S.Toleikis M.Z.Mo S.H.Glenzer | 2021 | Matter and Radiation at Extremes2021，6，5： | 0 |
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