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Subject: Diamonds ×

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    Measurement 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.
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    Magnetic field and angle-dependent photoluminescence of a fiber-coupled nitrogen vacancy rich diamond
    (Melville, NY : American Inst. of Physics, 2021) Wunderlich, Ralf; Staacke, Robert; Knolle, Wolfgang; Abel, Bernd; Meijer, Jan
    Here, we investigate the magnetic field dependent photoluminescence (PL) of a fiber-coupled diamond single crystal with a high density of nitrogen vacancy (NV) centers. Angle-dependent magnetic field sweep measurements between 0 and 111 mT were performed using an oscillating illumination combined with lock-in techniques. Besides the expected superposed PL of differently oriented NV centers, a zoo of features in the PL are found. These features can be associated with level anti-crossings and cross relaxations. In particular, PL measurements allowed us to detect auto-cross relaxation between coupled NV centers. Moreover, the PL measurements at low magnetic fields show dips suggesting an interaction of NV centers with additional spin defects. The results presented here are not only a study for NV-based fiber-coupled sensors made of diamond, but also show a way to investigate with manageable effort and purely an optical multispin interaction with at least one NV center as a constituent.