Detection of a single cobalt microparticle with a microfabricated atomic magnetometer

We present magnetic detection of a single, 2 {\mu}m diameter cobalt microparticle using an atomic magnetometer based on a microfabricated vapor cell. These results represent an improvement by a factor of 105 in terms of the detected magnetic moment over previous work using atomic magnetometers to detect magnetic microparticles. The improved sensitivity is due largely to the use of small vapor cells. In an optimized setup, we predict detection limits of 0.17 {\mu}m^3.Comment: 3 pages, 3 figure

Measurement of Untruncated Nuclear Spin Interactions via Zero- to Ultra-Low-Field Nuclear Magnetic Resonance

Zero- to ultra-low-field nuclear magnetic resonance (ZULF NMR) provides a new regime for the measurement of nuclear spin-spin interactions free from effects of large magnetic fields, such as truncation of terms that do not commute with the Zeeman Hamiltonian. One such interaction, the magnetic dipole-dipole coupling, is a valuable source of spatial information in NMR, though many terms are unobservable in high-field NMR, and the coupling averages to zero under isotropic molecular tumbling. Under partial alignment, this information is retained in the form of so-called residual dipolar couplings. We report zero- to ultra-low-field NMR measurements of residual dipolar couplings in acetonitrile-2-$^{13}$C aligned in stretched polyvinyl acetate gels. This represents the first investigation of dipolar couplings as a perturbation on the indirect spin-spin $J$-coupling in the absence of an applied magnetic field. As a consequence of working at zero magnetic field, we observe terms of the dipole-dipole coupling Hamiltonian that are invisible in conventional high-field NMR. This technique expands the capabilities of zero- to ultra-low-field NMR and has potential applications in precision measurement of subtle physical interactions, chemical analysis, and characterization of local mesoscale structure in materials.Comment: 6 pages, 3 figure

Long-lived heteronuclear spin-singlet states

We report observation of long-lived spin-singlet states in a 13C-1H spin pair at zero magnetic field. In 13C-labeled formic acid, we observe spin-singlet lifetimes as long as 37 seconds, about a factor of three longer than the T1 lifetime of dipole polarization in the triplet state. We also observe that the lifetime of the singlet-triplet coherence, T2, is longer than T1. Moreover, we demonstrate that this singlet states formed by spins of a heteronucleus and a 1H nucleus, can exhibit longer lifetimes than the respective triplet states in systems consisting of more than two nuclear spins. Although long-lived homonuclear spin-singlet states have been extensively studied, this is the first experimental observation of analogous spin-singlets consisting of a heteronucleus and a proton.Comment: 5 pages, 4 figure

Long-lived heteronuclear spin-singlet states

We report observation of long-lived spin-singlet states in a 13C-1H spin pair at zero magnetic field. In 13C-labeled formic acid, we observe spin-singlet lifetimes as long as 37 seconds, about a factor of three longer than the T1 lifetime of dipole polarization in the triplet state. We also observe that the lifetime of the singlet-triplet coherence, T2, is longer than T1. Moreover, we demonstrate that this singlet states formed by spins of a heteronucleus and a 1H nucleus, can exhibit longer lifetimes than the respective triplet states in systems consisting of more than two nuclear spins. Although long-lived homonuclear spin-singlet states have been extensively studied, this is the first experimental observation of analogous spin-singlets consisting of a heteronucleus and a proton

High-Resolution Zero-Field NMR <i>J</i>‑Spectroscopy of Aromatic Compounds

We report the acquisition and interpretation of nuclear magnetic resonance (NMR) <i>J</i>-spectra at zero magnetic field for a series of benzene derivatives, demonstrating the analytical capabilities of zero-field NMR. The zeroth-order spectral patterns do not overlap, which allows for straightforward determination of the spin interactions of substituent functional groups. Higher-order effects cause additional line splittings, revealing additional molecular information. We demonstrate resonance linewidths as narrow as 11 mHz, permitting resolution of minute frequency differences and precise determination of long-range <i>J</i>-couplings. The measurement of <i>J</i>-couplings with the high precision offered by zero-field NMR may allow further refinements in the determination of molecular structure and conformation

High-Resolution Zero-Field NMR <i>J</i>‑Spectroscopy of Aromatic Compounds

We report the acquisition and interpretation of nuclear magnetic resonance (NMR) <i>J</i>-spectra at zero magnetic field for a series of benzene derivatives, demonstrating the analytical capabilities of zero-field NMR. The zeroth-order spectral patterns do not overlap, which allows for straightforward determination of the spin interactions of substituent functional groups. Higher-order effects cause additional line splittings, revealing additional molecular information. We demonstrate resonance linewidths as narrow as 11 mHz, permitting resolution of minute frequency differences and precise determination of long-range <i>J</i>-couplings. The measurement of <i>J</i>-couplings with the high precision offered by zero-field NMR may allow further refinements in the determination of molecular structure and conformation

High-Resolution Zero-Field NMR <i>J</i>‑Spectroscopy of Aromatic Compounds

We report the acquisition and interpretation of nuclear magnetic resonance (NMR) <i>J</i>-spectra at zero magnetic field for a series of benzene derivatives, demonstrating the analytical capabilities of zero-field NMR. The zeroth-order spectral patterns do not overlap, which allows for straightforward determination of the spin interactions of substituent functional groups. Higher-order effects cause additional line splittings, revealing additional molecular information. We demonstrate resonance linewidths as narrow as 11 mHz, permitting resolution of minute frequency differences and precise determination of long-range <i>J</i>-couplings. The measurement of <i>J</i>-couplings with the high precision offered by zero-field NMR may allow further refinements in the determination of molecular structure and conformation

Zero-Field NMR Enhanced by Parahydrogen in Reversible Exchange

We have recently demonstrated that sensitive and chemically specific NMR spectra can be recorded in the absence of a magnetic field using hydrogenative parahydrogen induced polarization (PHIP)− and detection with an optical atomic magnetometer. Here, we show that non-hydrogenative parahydrogen-induced polarization− (NH-PHIP) can also dramatically enhance the sensitivity of zero-field NMR. We demonstrate the detection of pyridine, at concentrations as low as 6 mM in a sample volume of 250 μL, with sufficient sensitivity to resolve all identifying spectral features, as supported by numerical simulations. Because the NH-PHIP mechanism is nonreactive, operates in situ, and eliminates the need for a prepolarizing magnet, its combination with optical atomic magnetometry will greatly broaden the analytical capabilities of zero-field and low-field NMR