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- ItemMeasurement of diamond nucleation rates from hydrocarbons at conditions comparable to the interiors of icy giant planets(Woodbury, NY : Inst., 2020) Schuster, A.K.; Hartley, N.J.; Vorberger, J.; Döppner, T.; Van Driel, T.; Falcone, R.W.; Fletcher, L.B.; Frydrych, S.; Galtier, E.; Gamboa, E.J.; Gericke, D.O.; Glenzer, S.H.; Granados, E.; MacDonald, M.J.; MacKinnon, A.J.; McBride, E.E.; Nam, I.; Neumayer, P.; Pak, A.; Prencipe, I.; Voigt, K.; Saunders, A.M.; Sun, P.; Kraus, D.We present measurements of the nucleation rate into a diamond lattice in dynamically compressed polystyrene obtained in a pump-probe experiment using a high-energy laser system and in situ femtosecond x-ray diffraction. Different temperature-pressure conditions that occur in planetary interiors were probed. For a single shock reaching 70 GPa and 3000 K no diamond formation was observed, while with a double shock driving polystyrene to pressures around 150 GPa and temperatures around 5000 K nucleation rates between 1029 and 1034m-3 s-1 were recorded. These nucleation rates do not agree with predictions of the state-of-the-art theoretical models for carbon-hydrogen mixtures by many orders of magnitude. Our data suggest that there is significant diamond formation to be expected inside icy giant planets like Neptune and Uranus. © 2020 authors. Published by the American Physical Society.