A5032609026- Atomic and Subatomic Physics Research
- Advanced NMR Techniques and Applications
- Solid-state spectroscopy and crystallography
- Quantum, superfluid, helium dynamics
- NMR spectroscopy and applications
- Advanced MRI Techniques and Applications
- Quantum optics and atomic interactions
- Cold Atom Physics and Bose-Einstein Condensates
- Electron Spin Resonance Studies
- Nuclear Physics and Applications
- Dust and Plasma Wave Phenomena
- Advanced Frequency and Time Standards
- Plasma Diagnostics and Applications
- Rare-earth and actinide compounds
- Iron-based superconductors research
- Laser-induced spectroscopy and plasma
- Magnetic Field Sensors Techniques
- Geophysics and Sensor Technology
- Geophysical and Geoelectrical Methods
- Laser-Plasma Interactions and Diagnostics
- Magnetic properties of thin films
- Spectroscopy and Quantum Chemical Studies
- Earthquake Detection and Analysis
- Quantum and electron transport phenomena
- Electrical and Bioimpedance Tomography
George Mason University
2014-2024
United States Naval Research Laboratory
2001-2015
Naval Research Laboratory Chemistry Division
2011
École Normale Supérieure - PSL
1999-2001
Laboratoire Kastler Brossel
2000-2001
Princeton University
1996-1998
Acatech
1969
A method is described for producing several liters of nuclear spin polarized 129Xe gas via exchange with an optically pumped Rb vapor. We use a 140 W AlGaAs laser diode array whose broad spectral output efficiently absorbed by employing ∼10 atm 4He to pressure broaden the D1 absorption profile. in continuous flow and then cryogenically accumulated stored. Extensions this technique should enable production tens polarization order 50%. Production laser-polarized liter quantities important...
Using a new method of xenon laser-polarization that permits the generation liter quantities hyperpolarized 129Xe gas, first imaging results from human chest and spectroscopy head have been obtained. With polarization levels approximately 2%, cross-sectional images lung gas-spaces with voxel volume 0.9 cm3 (signal-to-noise ratio (SNR), 28) were acquired three dissolved-phase resonances in spectra detected. In head, one prominent resonance, presumably brain parenchyma, was anticipated...
We describe an alkali-metal magnetometer for detection of weak magnetic fields in the radio-frequency (rf) range. High sensitivity is achieved by tuning Zeeman resonance alkali atoms to rf frequency and partially suppressing spin-exchange collisions vapor. demonstrate field $2\text{ }\text{ }\mathrm{fT}/{\mathrm{Hz}}^{1/2}$ at a 99 kHz with width 400 Hz. also derive simple analytic expression fundamental limit on show that about $0.01\text{ can be practical system measurement volume...
A radio-frequency tunable atomic magnetometer is developed for detection of nuclear quadrupole resonance (NQR) from room temperature solids. It has a field sensitivity 0.24fT∕Hz1∕2 at the 423kHz N14 NQR frequency ammonium nitrate. potential application nitrogen-containing explosives which difficult with conventional tuned copper coils due to poor signal-to-noise ratio (SNR) below few megahertz. The signal 22g powdered nitrate located 2cm away sensor detected SNR 9 in 4.4-s-long multiple echo...
Whether in medical or security applications, magnetic resonance spectroscopy is very useful for detecting faint signals from target compounds. However, interference (from $e.g.$ a local radio station) can be problem. The authors devise optical atomic-gas detectors that work unshielded environments, and without cryogenic cooling---important advantages real-world use. These sensitive, compact systems offer baseline noise at the quantum limit.
We demonstrate a radio-frequency potassium-vapor magnetometer operating with sensitivities of 0.3 fT/Hz at 0.5 MHz and 0.9 1.31 in the absence mu-metal or magnetic shielding. The use spatially separated magnetometers, two voxels within same cell, permits for subtraction common mode noise retention gradient signal, as from local source. At was white measured to be 3.4 fT/Hz; upon returned values observed when shielded. MHz, nearby radio station reduced by factor 33 subtraction, limited only...
The deviation of the electron density around nuclei from spherical symmetry determines electric field gradient (EFG), which can be measured by various types spectroscopy. Nuclear Quadrupole Resonance (NQR) is particularly sensitive to EFG. EFGs, and implication NQR frequencies, vary dramatically across materials. Consequently, searching for spectral lines in previously uninvestigated materials represents a major challenge. Calculated EFGs significantly aid at search inception. To facilitate...
The authors develop two optically pumped atomic magnetometers with sub-fT sensitivity operating at radio frequencies and compare their magnetic-field interference rejection. They identify ways to improve the of unshielded magnetic detectors, which could advance development portable for field uses.
We show, theoretically and experimentally, how the absolute orientation polarization state of radio-frequency (rf) magnetic fields in a transverse two-dimensional (2D) plane can be uniquely determined using two optically pumped atomic magnetometers. In addition, output signals from these quantum sensors readily expressed as Jones vector. This composite device complement electric field detection finding rf directions or it used applications where is negligible. The latter found myriad source...
To study how highly magnetized liquids behave in NMR experiments, we have performed low-field on laser-polarized liquid ${}^{129}\mathrm{Xe},$ with nuclear polarization of up to 6%. Contrary conventional results, find that instabilities develop after a large pulse, leading an unexpectedly abrupt decay the signal. In contrast, spectrum small pulse collapses series unusually sharp lines (spectral clustering), whose widths correspond precession lifetimes longer than half minute. We discuss key...
There are a number of mechanisms that can produce frequency shifts in the NMR spectra optically pumped semiconductors, including hyperfine interaction, nuclear dipolar fields, and indirect or $J$ couplings. Using Fe-doped InP, we explore how to experimentally distinguish these shift from one another, then exploit measure absolute polarization. Furthermore, pump, using circularly polarized light, at much lower field (2.35 T) than previous work, permitting us dependence polarization rate,...
Under negative feedback, the quality factor Q of a radio-frequency magnetometer can be decreased by more than two orders magnitude, so that any initial perturbation polarized spin system rapidly damped, preparing for detection desired signal. We find noise is also suppressed under such spin-damping, with characteristic spectral response corresponding to type noise; therefore magnetic, photon-shot, and spin-projection measured distinctly. While suppression resonant photon-shot implies...
We demonstrate, theoretically and experimentally, that the irradiation of a powder sample containing spin-1 nuclei by two three characteristic nuclear quadrupole resonance (NQR) frequencies can result in several echo signals at third NQR frequency. One these echoes, principal echo, has same shape time occurrence as an produced after pair single-frequency excitations. The other echoes are not equivalent to any echo. These secondary focus this paper. determined correlation distribution one...
Unexpectedly, we observe a strong Gaussian decay in the nuclear quadrupole resonance signal obtained from powder sample of spin-1 nuclei under perturbation by off-resonant radio frequency pulses. Using model composed just pairs nuclei, theoretically determine that is due to homonuclear dipolar coupling being selectively unrefocused We find rate measures coupling's strength and permits us how much sample's linewidth versus electric-field gradient inhomogeneity. Furthermore, knowing strength,...
We theoretically examine the perturbative effects of a series radio-frequency (rf) pulses, electric field gradient inhomogeneity, and dipole-dipole coupling on spin dynamics spin-1 nuclei dominated by quadrupole interaction. The is between neighboring with identical nuclear resonance frequencies, but principal axes frames at each nucleus are not aligned. Such comprehensive treatment necessary to determine optimal sequence rf pulses which maximizes echoes in detection substance interest, for...
We report the results of experiments leading to production an image a polarized Xe129 sample prepared by spin exchange with Cs, optically pumped spectrally narrowed 894.3 nm diode laser. Representative images average electron polarization are shown. Appreciable cesium values were achieved, and nuclear about 2.5% was measured for The absolute water-calibrated free induction decay magnetic resonance signal, xenon imaged using 2 T imaging system.
Using double-resonance conditions, in which the Larmor frequency of a spin-1∕2 nucleus is matched to one nuclear quadrupole resonance frequencies spin-1 nucleus, authors demonstrate increased cross relaxation between two spin species. They calculate cross-relaxation rate using motionally averaged heterogeneous dipole Hamiltonian as perturbation combined and Zeeman Hamiltonians. this rate, addition hydrogen nitrogen autorelaxation rates, expressions governing spin-lattice are determined. With...