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Evidence for a glassy state in strongly driven carbon.

Brown CR, Gericke DO, Cammarata M, Cho BI, Döppner T, Engelhorn K, Förster E, Fortmann C, Fritz D, Galtier E, Glenzer SH, Harmand M, Heimann P, Kugland NL, Lamb DQ, Lee HJ, Lee RW, Lemke H, Makita M, Moinard A, Murphy CD, Nagler B, Neumayer P, Plagemann KU, Redmer R, Riley D, Rosmej FB, Sperling P, Toleikis S, Vinko SM, Vorberger J, White S, White TG, Wünsch K, Zastrau U, Zhu D, Tschentscher T, Gregori G - Sci Rep (2014)

Bottom Line: Here, we report results of an experiment creating a transient, highly correlated carbon state using a combination of optical and x-ray lasers.Scattered x-rays reveal a highly ordered state with an electrostatic energy significantly exceeding the thermal energy of the ions.The experiment suggests a much slower nucleation and points to an intermediate glassy state where the ions are frozen close to their original positions in the fluid.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK [2] Plasma Physics Department, AWE plc., Aldermaston, Reading RG7 4PR, UK [3] Plasma Physics Group, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ, UK.

ABSTRACT
Here, we report results of an experiment creating a transient, highly correlated carbon state using a combination of optical and x-ray lasers. Scattered x-rays reveal a highly ordered state with an electrostatic energy significantly exceeding the thermal energy of the ions. Strong Coulomb forces are predicted to induce nucleation into a crystalline ion structure within a few picoseconds. However, we observe no evidence of such phase transition after several tens of picoseconds but strong indications for an over-correlated fluid state. The experiment suggests a much slower nucleation and points to an intermediate glassy state where the ions are frozen close to their original positions in the fluid.

No MeSH data available.


Related in: MedlinePlus

Structure factor of strongly coupled carbon.Panel a: scattering data from the un-shocked (cold) graphite. The position and relative intensity of the bcc lattice peaks, labelled according their Miller indices, for ρ = 2.5 g/cm3 (blue lines) and ρ = 4.5 g/cm3 (orange lines) is indicated in the figure. The Bragg peak intensity is estimated by assuming ηΓ = 0.1. Panel b: data were collected at a repetition rate of approximately a shot per 10 seconds, allowing for the coherent scattering to be taken at various combinations of beam delays and measurement angle. Each data point consists of an average of about 50–60 individual shots. The FEL energy has been individually recorded for each shot, and then single spectra have been weighted by the corresponding energy in the FEL beam (with cold scattering removed). The experimental values for Sii(k) were derived from the total elastic scattering by assuming Z = 4.5 ± 0.5. The uncertainty in Z determines the vertical error bars. The standard deviation in signal intensity from shot-to-shot variations in a data set is within the reported errors. Horizontal error bar are related to the finite acceptance angle of the spectrometer. The calculated curves are results from a fluid model for charged ions embedded in a polarisable background of electrons for a density of ρ = 2.5 g/cm3 and ρ = 4.5 g/cm3, an ion charge state of Z = 4.5, and two different temperatures (1 eV equals 11,600 K). Panel c: plot of versus T and Z, where  is the structure factor derived from the measured data (Iexp) and  is the calculation for ρ = 2.5 g/cm3, θ = 50° and 40 ps delay.
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f3: Structure factor of strongly coupled carbon.Panel a: scattering data from the un-shocked (cold) graphite. The position and relative intensity of the bcc lattice peaks, labelled according their Miller indices, for ρ = 2.5 g/cm3 (blue lines) and ρ = 4.5 g/cm3 (orange lines) is indicated in the figure. The Bragg peak intensity is estimated by assuming ηΓ = 0.1. Panel b: data were collected at a repetition rate of approximately a shot per 10 seconds, allowing for the coherent scattering to be taken at various combinations of beam delays and measurement angle. Each data point consists of an average of about 50–60 individual shots. The FEL energy has been individually recorded for each shot, and then single spectra have been weighted by the corresponding energy in the FEL beam (with cold scattering removed). The experimental values for Sii(k) were derived from the total elastic scattering by assuming Z = 4.5 ± 0.5. The uncertainty in Z determines the vertical error bars. The standard deviation in signal intensity from shot-to-shot variations in a data set is within the reported errors. Horizontal error bar are related to the finite acceptance angle of the spectrometer. The calculated curves are results from a fluid model for charged ions embedded in a polarisable background of electrons for a density of ρ = 2.5 g/cm3 and ρ = 4.5 g/cm3, an ion charge state of Z = 4.5, and two different temperatures (1 eV equals 11,600 K). Panel c: plot of versus T and Z, where is the structure factor derived from the measured data (Iexp) and is the calculation for ρ = 2.5 g/cm3, θ = 50° and 40 ps delay.

Mentions: As plotted in the inset of Figure 1, the scattered radiation shows two distinct features: i) an elastic (or nearly elastic) peak at the original wavelength, and ii) a frequency-shifted feature. The first feature is the result of scattering by electrons that kinematically follow the ions2122, which in WDM can be bound or form the screening cloud around the ions. The second feature, which is smaller in intensity but still contributing a significant amount of the total signal (see Figure 1), results from inelastic scattering off free electrons and Compton scattering from core electrons which causes photo-ionization. We used a highly oriented pyrolitic graphite (HOPG) crystal analyzer23 in order to separate the elastic from the inelastic scattering. The measured spectra were furthermore deconvolved by taking into account the measured spectral profile of the FEL source. Any diffuse scattering arising from the polycrystalline structure of the cold (un-shocked) region of sample is removed by subtracting the measured scattering signal without optical laser heating (i.e., FEL only) weighted by the mass fraction of unshocked material. At any given time the latter is estimated from the results of a radiation-hydrodynamics simulation (see Figure 2). The cold scattering signal is plotted in Figure 3a. The cold graphite structure is hexagonal close-packed (hcp). The (012) diffraction line contributes to the measured peak at 3.4 Å−1 (θ = 50°).


Evidence for a glassy state in strongly driven carbon.

Brown CR, Gericke DO, Cammarata M, Cho BI, Döppner T, Engelhorn K, Förster E, Fortmann C, Fritz D, Galtier E, Glenzer SH, Harmand M, Heimann P, Kugland NL, Lamb DQ, Lee HJ, Lee RW, Lemke H, Makita M, Moinard A, Murphy CD, Nagler B, Neumayer P, Plagemann KU, Redmer R, Riley D, Rosmej FB, Sperling P, Toleikis S, Vinko SM, Vorberger J, White S, White TG, Wünsch K, Zastrau U, Zhu D, Tschentscher T, Gregori G - Sci Rep (2014)

Structure factor of strongly coupled carbon.Panel a: scattering data from the un-shocked (cold) graphite. The position and relative intensity of the bcc lattice peaks, labelled according their Miller indices, for ρ = 2.5 g/cm3 (blue lines) and ρ = 4.5 g/cm3 (orange lines) is indicated in the figure. The Bragg peak intensity is estimated by assuming ηΓ = 0.1. Panel b: data were collected at a repetition rate of approximately a shot per 10 seconds, allowing for the coherent scattering to be taken at various combinations of beam delays and measurement angle. Each data point consists of an average of about 50–60 individual shots. The FEL energy has been individually recorded for each shot, and then single spectra have been weighted by the corresponding energy in the FEL beam (with cold scattering removed). The experimental values for Sii(k) were derived from the total elastic scattering by assuming Z = 4.5 ± 0.5. The uncertainty in Z determines the vertical error bars. The standard deviation in signal intensity from shot-to-shot variations in a data set is within the reported errors. Horizontal error bar are related to the finite acceptance angle of the spectrometer. The calculated curves are results from a fluid model for charged ions embedded in a polarisable background of electrons for a density of ρ = 2.5 g/cm3 and ρ = 4.5 g/cm3, an ion charge state of Z = 4.5, and two different temperatures (1 eV equals 11,600 K). Panel c: plot of versus T and Z, where  is the structure factor derived from the measured data (Iexp) and  is the calculation for ρ = 2.5 g/cm3, θ = 50° and 40 ps delay.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4048912&req=5

f3: Structure factor of strongly coupled carbon.Panel a: scattering data from the un-shocked (cold) graphite. The position and relative intensity of the bcc lattice peaks, labelled according their Miller indices, for ρ = 2.5 g/cm3 (blue lines) and ρ = 4.5 g/cm3 (orange lines) is indicated in the figure. The Bragg peak intensity is estimated by assuming ηΓ = 0.1. Panel b: data were collected at a repetition rate of approximately a shot per 10 seconds, allowing for the coherent scattering to be taken at various combinations of beam delays and measurement angle. Each data point consists of an average of about 50–60 individual shots. The FEL energy has been individually recorded for each shot, and then single spectra have been weighted by the corresponding energy in the FEL beam (with cold scattering removed). The experimental values for Sii(k) were derived from the total elastic scattering by assuming Z = 4.5 ± 0.5. The uncertainty in Z determines the vertical error bars. The standard deviation in signal intensity from shot-to-shot variations in a data set is within the reported errors. Horizontal error bar are related to the finite acceptance angle of the spectrometer. The calculated curves are results from a fluid model for charged ions embedded in a polarisable background of electrons for a density of ρ = 2.5 g/cm3 and ρ = 4.5 g/cm3, an ion charge state of Z = 4.5, and two different temperatures (1 eV equals 11,600 K). Panel c: plot of versus T and Z, where is the structure factor derived from the measured data (Iexp) and is the calculation for ρ = 2.5 g/cm3, θ = 50° and 40 ps delay.
Mentions: As plotted in the inset of Figure 1, the scattered radiation shows two distinct features: i) an elastic (or nearly elastic) peak at the original wavelength, and ii) a frequency-shifted feature. The first feature is the result of scattering by electrons that kinematically follow the ions2122, which in WDM can be bound or form the screening cloud around the ions. The second feature, which is smaller in intensity but still contributing a significant amount of the total signal (see Figure 1), results from inelastic scattering off free electrons and Compton scattering from core electrons which causes photo-ionization. We used a highly oriented pyrolitic graphite (HOPG) crystal analyzer23 in order to separate the elastic from the inelastic scattering. The measured spectra were furthermore deconvolved by taking into account the measured spectral profile of the FEL source. Any diffuse scattering arising from the polycrystalline structure of the cold (un-shocked) region of sample is removed by subtracting the measured scattering signal without optical laser heating (i.e., FEL only) weighted by the mass fraction of unshocked material. At any given time the latter is estimated from the results of a radiation-hydrodynamics simulation (see Figure 2). The cold scattering signal is plotted in Figure 3a. The cold graphite structure is hexagonal close-packed (hcp). The (012) diffraction line contributes to the measured peak at 3.4 Å−1 (θ = 50°).

Bottom Line: Here, we report results of an experiment creating a transient, highly correlated carbon state using a combination of optical and x-ray lasers.Scattered x-rays reveal a highly ordered state with an electrostatic energy significantly exceeding the thermal energy of the ions.The experiment suggests a much slower nucleation and points to an intermediate glassy state where the ions are frozen close to their original positions in the fluid.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK [2] Plasma Physics Department, AWE plc., Aldermaston, Reading RG7 4PR, UK [3] Plasma Physics Group, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ, UK.

ABSTRACT
Here, we report results of an experiment creating a transient, highly correlated carbon state using a combination of optical and x-ray lasers. Scattered x-rays reveal a highly ordered state with an electrostatic energy significantly exceeding the thermal energy of the ions. Strong Coulomb forces are predicted to induce nucleation into a crystalline ion structure within a few picoseconds. However, we observe no evidence of such phase transition after several tens of picoseconds but strong indications for an over-correlated fluid state. The experiment suggests a much slower nucleation and points to an intermediate glassy state where the ions are frozen close to their original positions in the fluid.

No MeSH data available.


Related in: MedlinePlus