Research ArticleAPPLIED PHYSICS

Magnetic flux tailoring through Lenz lenses for ultrasmall samples: A new pathway to high-pressure nuclear magnetic resonance

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Science Advances  08 Dec 2017:
Vol. 3, no. 12, eaao5242
DOI: 10.1126/sciadv.aao5242
  • Fig. 1 Schematic explosion diagram of the resonator setup and the anvil/gasket arrangement.

    The blue and red arrows denote the directions of the external magnetic field B0 and the RF magnetic field B1, respectively, generated by the excitation coil and the lens, which is compressed between the rhenium gasket and the 800-μm culeted diamond anvil. The enlarged picture shows the RF arrangement of the excitation coil with the Lenz lens. Black arrows denote the directions of the high-frequency current.

  • Fig. 2 Sensitivity and stability tests of the Lenz lens resonator setup in a DAC.

    (A) Proton spectra of paraffin at ambient pressure with and without the use of a Lenz lens. (B) Photographs of different deformation states of the lens under pressure. Black contours are guide to the eye. (C) Recorded 1H NMR spectra. At ambient conditions, 100 scans were accumulated, whereas at higher pressures, only single-shot spectra after a single π/2 pulse were recorded. (D) Pressure dependence of the FWHM linewidths. The dotted line denotes the crystallization pressure at ambient temperature, and the shaded areas denote the liquid and amorphous phases of paraffin. The glass transition pressure was obtained from other methods.

  • Fig. 3 LODt at increasing pressures obtained from microcoil experiments and from Lenz lenses.

    The obtained gains in sensitivity and reachable pressures are indicated by black arrows.

  • Fig. 4 2D nutation spectroscopy experiments on paraffin oil up to 64 GPa.

    (A) In time domain, the obtained data consist of the direct dimension t1 of the free induction decays (FIDs) that correlated with the indirect dimension t2 defined by the incrementally increasing RF pulse lengths. Fourier transform (FT) in both dimensions yields the 2D nutation spectrum. (B) Comparison of obtained 2D nutation spectra of paraffin at pressures up to 64 GPa. All spectra are normalized relative to 8 GPa, thus evidencing a loss in total NMR signal intensity. (C) Summary of 2D intensities for both spectral species and the total intensity. The nutation spectra were acquired at 16-W pulse power.

  • Table 1 Summary of performance data using an inductively coupled Lenz lens resonator.

    The average pressure, p, was obtained at the center of the 250-μm culeted diamond anvil. The 90° pulse lengths, tπ/2, were obtained by nutation experiments at 1-W pulse power and used to estimate the average RF magnetic field strengths 〈B1〉. LODt was estimated given the obtained time-domain SNR, SNRt, a number of about Embedded Image hydrogen nuclei in the sample cavity, and a receiver bandwidth of 2 MHz at all measurements.

    p (GPa)tπ/2
    (μs)
    B1
    (mT)
    SNRtLODt
    (spins/Embedded Image)
    10−42.42.5196 × 1011
    12.13.018.27 × 1011
    71.93.116.57.3 × 1011
    192.52.314.28.5 × 1011
    342.22.7158 × 1011
    491.83.3101.2 × 1012
    642.22.771.7 × 1012
    722.32.681.5 × 1012

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/12/eaao5242/DC1

    fig. S1. SEM image of the 250-μm anvil with the 100-μm recess.

    fig. S2. Raman spectra used for pressure determination.

    fig. S3. RF characterisation of the resonator.

    fig. S4. 1H NMR spectra.

    fig. S5. Magnetic field maps of the B1 fields generated by a microcoil of four turns (400 μm in diameter and 100 μm in height, left) and of a flat Lenz lens made from a solid sheet of gold foil (right).

    fig. S6. 1H-1H COSY spectrum of thymine in a pressure cell at pressures close to the pressure-induced freezing point of the D2O solvent.

    fig. S7. 1H NMR spectra.

    section S1. 1H NMR on ice VII up to 17 GPa.

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. SEM image of the 250-μm anvil with the 100-μm recess.
    • fig. S2. Raman spectra used for pressure determination.
    • fig. S3. RF characterization of the resonator.
    • fig. S4. 1H NMR spectra.
    • fig. S5. Magnetic field maps of the B1 fields generated by a microcoil of four turns (400 μm in diameter and 100 μm in height, left) and of a flat Lenz lens made from a solid sheet of gold foil (right).
    • fig. S6. 1H-1H COSY spectrum of thymine in a pressure cell at pressures close to the pressure-induced freezing point of the D2O solvent.
    • fig. S7. 1H NMR spectra.
    • section S1. 1H NMR on ice VII up to 17 GPa.

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