An optical NMR spectrometer for Larmor-beat detection and high-resolution POWER NMR

Kempf, James; Marohn, John A.; Carson, Paul J.; Shykind, David; Hwang, J. Y.; Miller, Michael A.; Weitekamp, D. P.

doi:10.1063/1.2936257

Cited by 6 publications

(13 citation statements)

References 31 publications

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“…The alignment of NMR quantization axes with respect to the sample frame can be optimized separately for each task (ONP, t 1 , and optical detection) by electronically reorienting the applied static magnetic field B 0 (22). For ONP, B 0 is along the [001] crystal axis.…”

Section: The Optical and Power Nmr Combinationmentioning

confidence: 99%

“…In both SI Methods and ref. 22, we detail the sample, apparatus, and NMR parameters, as well as protocols for LBD optical and POWER NMR.…”

Section: Methodsmentioning

confidence: 99%

“…4B, whereas the range (r/a* 0 ) ϭ 0.5-2.0 corresponds to ⌬r from 0.2 to 3.6 nm. If instead, one assumes the best spectral resolution (⌬ ϭ 4 Hz) we have obtained with this technique and sample (22), the entire image would exceed atomic-resolution (dashed curve in Fig. 4B).…”

Section: Quantifying the Nanoscale Distribution Of Electron Spinmentioning

confidence: 99%

“…RF irradiation of nonsignal nuclei is not shown. Breaks in the timeline can accommodate events such as adiabatic reorientation of the magnetic field (22). Saturation delays were d Ϸ 1.5 ms.…”

Section: Figmentioning

confidence: 99%

“…This quantity is modulated by magnetic fields (including hyperfine fields of nuclear origin) that are transverse to the optical axis through the Hanle effect (2). In particular, we use the Larmor-beat detection (LBD) method (9,22), whereby is modulated by the transverse magnetization of signal (e.g., 71 Ga or 69 Ga) and reference (e.g., 75 As) nuclei. This variant of Hanle-effect optical detection has the advantages of providing an rf photocurrent linear in the precessing signal magnetization.…”

Section: The Optical and Power Nmr Combinationmentioning

confidence: 99%

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Imaging quantum confinement with optical and POWER (perturbations observed with enhanced resolution) NMR

Kempf

Miller

Weitekamp

2008

Proc. Natl. Acad. Sci. U.S.A.

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The nanoscale distributions of electron density and electric fields in GaAs semiconductor devices are displayed with NMR experiments. The spectra are sensitive to the changes to the nuclear-spin Hamiltonian that are induced by perturbations delivered in synchrony with a line-narrowing pulse sequence. This POWER (perturbations observed with enhanced resolution) method enhanced resolution up to 10 3 -fold, revealing the distribution of perturbations over nuclear sites. Combining this method with optical NMR, we imaged quantum-confined electron density in an individual AlGaAs/GaAs heterojunction via hyperfine shifts. Fits to the coherent evolution and relaxation of nuclei within a hydrogenic state established one-to-one correspondence of radial position to frequency. Further experiments displayed the distribution of photoinduced electric field within the same states via a quadrupolar Stark effect. These unprecedented high-resolution distributions discriminate between competing models for the luminescence and support an excitonic state, perturbed by the interface, as the dominant source of the magnetically modulated luminescence.GaAs ͉ hyperfine or Knight shift ͉ Stark effect ͉ H-band photoluminescence I maging electron distributions and the electrostatic potentials that govern their transfer is a longstanding goal in diverse fields. Spin or charge transfer defines function in systems for photovoltaic and photosynthetic energy capture, ion channels, enzyme catalysis, spintronics, and molecular and nanoscale electronics. Success in imaging nanoscale electronic properties can lead to mechanistic understanding and provide guidelines to tune device performance or to modify natural systems for specialized applications. With its atomic-scale capabilities for nondestructive, noninvasive spectroscopy and imaging, NMR seems well suited to such characterization. However, NMR of solids is hampered by broad spectral lines because of static interactions that prevent measurement of small differences between sites that might otherwise reveal local electronic features with atomic detail.Here, we present a general method whereby solid-state NMR surmounts this challenge and then apply it to image distributions of spin density and electric (E) field within an electronic state with dimensions (Ϸ10 nm) distributed over Ϸ10 5 nuclei. The POWER (perturbations observed with enhanced resolution) NMR approach, encodes small responses to a sample perturbation that is switched in synchrony with an NMR multiple-pulse line-narrowing sequence. The sequence removes the otherwise obscuring clutter of static spin interactions to yield a spectrum dominated by the desired perturbation with up to 3 orders-ofmagnitude resolution enhancement. To further obtain the sensitivity and selectivity needed to isolate signals of local, nanoscale features from the bulk signal of a macroscopic sample, we combined the POWER approach with methods for optical NMR (ONMR). By using both optical nuclear polarization (ONP) (1-15) and optical detection (2-4, 6, 7, 9-13), O...

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Section: The Optical and Power Nmr Combinationmentioning

confidence: 99%

“…In both SI Methods and ref. 22, we detail the sample, apparatus, and NMR parameters, as well as protocols for LBD optical and POWER NMR.…”

Section: Methodsmentioning

confidence: 99%

Section: Quantifying the Nanoscale Distribution Of Electron Spinmentioning

confidence: 99%

Section: Figmentioning

confidence: 99%

Section: The Optical and Power Nmr Combinationmentioning

confidence: 99%

See 3 more Smart Citations

Imaging quantum confinement with optical and POWER (perturbations observed with enhanced resolution) NMR

Kempf

Miller

Weitekamp

2008

Proc. Natl. Acad. Sci. U.S.A.

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Enhancing time-suspension sequences for the measurement of weak perturbations

Tarasek

Goldfarb

Kempf

2011

Journal of Magnetic Resonance

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A System for NMR Stark Spectroscopy of Quadrupolar Nuclei

Tarasek¹,

Kempf²

2010

J. Phys. Chem. A

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Electrostatic influences on NMR parameters are well accepted. Experimental and computational routes have been long pursued to understand and utilize such Stark effects. However, existing approaches are largely indirect informants on electric fields, and/or are complicated by multiple causal factors in spectroscopic change. We present a system to directly measure quadrupolar Stark effects from an applied electric (E) field. Our apparatus and applications are relevant in two contexts. Each uses a radiofrequency (rf) E field at twice the nuclear Larmor frequency (2omega(0)). The mechanism is a distortion of the E-field gradient tensor that is linear in the amplitude (E(0)) of the rf E field. The first uses 2omega(0) excitation of double-quantum transitions for times similar to T(1) (the longitudinal spin relaxation time). This perturbs the steady state distribution of spin population. Nonlinear analysis versus E(0) can be used to determine the Stark response rate. The second context uses POWER (perturbations observed with enhanced resolution) NMR. Here, coherent, short-time (<

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An optical NMR spectrometer for Larmor-beat detection and high-resolution POWER NMR

Cited by 6 publications

References 31 publications

Imaging quantum confinement with optical and POWER (perturbations observed with enhanced resolution) NMR

Imaging quantum confinement with optical and POWER (perturbations observed with enhanced resolution) NMR

Enhancing time-suspension sequences for the measurement of weak perturbations

A System for NMR Stark Spectroscopy of Quadrupolar Nuclei

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