Theory of T1 relaxation measurements in pure nuclear quadrupole resonance for spins / = 1
01 Aug 1974-Journal of Chemical Physics (American Institute of Physics)-Vol. 61, Iss: 3, pp 1093-1100
TL;DR: In this article, the effect of spin lattice relaxation rates on pure quadrupole resonance pulse experiments for spins with I = 1 is given, in which the three dimensional relaxation problem is reduced to a two dimensional one.
Abstract: A quantitative analysis of the effect of spin lattice relaxation rates on pure quadrupole resonance pulse experiments for spins with I = 1 is given. A model is presented in which the three dimensional relaxation problem is reduced to a two dimensional one. In this model any possible population distribution of the energy levels corresponds to a point in a plane, the ``ν plane.'' The response of the system to spin‐lattice relaxation effects and to rf pulses are described as translations of points in this plane. The experimental signal intensities are directly related to the coordinates of those points. The following cases are treated quantitatively: (i) CW saturation, (ii) CW saturation followed by a 90° pulse, (iii) two‐pulse sequences, and (iv) continuous steady state pulse sequences. For each case explicit equations for the signal intensity as function of the experimental parameters are given. The analysis is made for both single crystals and powders.
Citations
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01 Jan 2008
TL;DR: In this paper, a spin exchange relaxation-free (SERF) magnetometer was proposed to measure all three vector components of the magnetic field in an unshielded environment with comparable sensitivity to other devices.
Abstract: Alkali-metal magnetometers use the coherent precession of polarized atomic spins to detect and measure magnetic fields. Recent advances have enabled magnetometers to become competitive with SQUIDs as the most sensitive magnetic field detectors, and they now find use in a variety of areas ranging from medicine and NMR to explosives detection and fundamental physics research. In this thesis we discuss several developments in alkali-metal atomic magnetometry for both practical and fundamental applications. We present a new method of polarizing the alkali atoms by modulating the optical pumping rate at both the linear and quadratic Zeeman resonance frequencies. We demonstrate experimentally that this method enhances the sensitivity of a potassium magnetometer operating in the Earth’s field by a factor of 4, and we calculate that it can reduce the orientation-dependent heading error to less than 0.1 nT. We discuss a radio-frequency magnetometer for detection of oscillating magnetic fields with sensitivity better than 0.2 fT/ √ Hz, which we apply to the observation of nuclear magnetic resonance (NMR) signals from polarized water, as well as nuclear quadrupole resonance (NQR) signals from ammonium nitrate. We demonstrate that a spin-exchange relaxation-free (SERF) magnetometer can measure all three vector components of the magnetic field in an unshielded environment with comparable sensitivity to other devices. We find that octadecyltrichlorosilane (OTS) acts as an anti-relaxation coating for alkali atoms at temperatures below 170◦C, allowing them to collide with a glass surface up to 2,000 times before depolarizing, and we present the first demonstration of high-temperature magnetometry with a coated cell. We also describe a reusable alkali vapor cell intended for the study of interactions between alkali atoms and surface coatings. Finally, we explore the use of a cesium-xenon SERF comagnetometer for a proposed measurement of the permanent electric dipole moments (EDMs) of the electron and the 129Xe atom, with projected sensitivity of δde=9×10−30 e-cm and δdXe=4×10−31 e-cm after 100 days of integration; both bounds are more than two orders of magnitude better than the existing experimental limits on the EDMs of the electron and of any diamagnetic atom.
232 citations
Cites background from "Theory of T1 relaxation measurement..."
...The signal varies as a Bessel function with the rf pulse strength (Vega, 1974)....
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...18(b) we show the NQR signal as a function of the strength of the rf excitation pulse, which varies as a Bessel function (Vega, 1974)....
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TL;DR: In this article, a radio-frequency tunable atomic magnetometer was developed for detection of nuclear quadrupole resonance (NQR) from room temperature solids, which has a field sensitivity 0.24fT∕Hz1∕2 at the 423kHz N14 NQR frequency of ammonium nitrate.
Abstract: 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 of ammonium nitrate. A potential application of the magnetometer is detection of nitrogen-containing explosives which is difficult with conventional tuned copper coils due to a poor signal-to-noise ratio (SNR) below a few megahertz. The NQR signal from 22g of powdered ammonium nitrate located 2cm away from the sensor is detected with a SNR of 9 in a 4.4-s-long multiple echo sequence, which represents an estimated order-of-magnitude improvement in sensitivity over the pickup coil detection.
160 citations
TL;DR: In this paper, a powder pattern simulation using an NQCC value of 5.027 MHz and an asymmetry parameter {eta} of 0.2 agrees reasonably well with the experimental stepped-frequency spectrum.
Abstract: Results from {sup 14}N pure NQR of cocaine in the free base form (cocaine base) yield a nuclear quadrupole coupling constant (NQCC) e{sup 2}Qq/h of 5.0229 ({+-}0.0001) MHz and an asymmetry parameter {eta} of 0.0395 ({+-}0.0001) at 295 K, with corresponding values of 5.0460 ({+-}0.0013) MHz and 0.0353 ({+-}0.0008) at 77 K. Both pure NQR (at 295-77 K) and a superconducting quantum interference device (SQUID) detector (at 4.2 K) were used to measure the very low (<1 MHz) {sup 14}N transition frequencies in cocaine hydrochloride; at 295 K the NQCC is 1.1780 ({+-}0.0014) MHz and the asymmetry parameter is 0.2632 ({+-}0.0034). Stepping the carrier frequency enables one to obtain a powder pattern without the severe intensity distortions that otherwise arise from finite pulse power. A powder pattern simulation using an NQCC value of 5.027 MHz and an asymmetry parameter {eta} of 0.2 agrees reasonably well with the experimental stepped-frequency spectrum. The use of pure NQR for providing nondestructive, quantitative, and highly specific detection of crystalline compounds is discussed, as are experimental strategies. 31 refs., 8 figs., 1 tab.
98 citations
TL;DR: In this paper, a meanderline with 11 conducting strips of 4 cm spacing was used to observe the 14N resonance line in sodium nitrite at sample distances up to 1.6 cm, where the RF field has dropped to less than 1e.
61 citations
Patent•
12 Jan 1998
TL;DR: In this article, the authors present an approach for testing a remote sample containing a given species of quadrupolar nucleus containing at least one probe (112) having a given maximum cross-sectional dimension.
Abstract: Apparatus for Nuclear Quadrupole Resonance testing a remote sample containing a given species of quadrupolar nucleus includes at least one probe (112) having a given maximum cross-sectional dimension; a device (102) for applying excitation to the probe or at least one of the probes to excite nuclear quadruple resonance for a selected range of distance of the sample from each such probe, the selected range being at least one tenth of the given maximum dimension of the probe, the apparatus being adapted to produce a non-uniform field over the selected range; and a device (106) for detecting the resonance response signal from the sample via the probe or at least one of the probes; the excitation being such as would generate non-zero resonance signals at all distances within the selected range.
58 citations
References
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575 citations
TL;DR: In this article, the theory of Spin-Gitterrelaxation in Molekulkristallen with Quadrupolkopplung is investigated. Butler et al. present an experimental and theoretisch ermittelten Grenzen fur die spin-gitter-relaxationszeitt 1.
Abstract: Die vorliegende Arbeit soll einen Beitrag zur Theorie der Spin-Gitterrelaxation in Molekulkristallen mit Quadrupolkopplung liefern. Es wird versucht, die Mesergebnisse vonDehmelt undKruger am Dichlorathylen (CHCl=CHCl) theoretisch zu deuten. Die schwache Temperaturabhangigkeit der Kernquadrupolresonanzfrequenz kann erklart werden, wenn man die Molekule im Gitterverband als quantenmechanische harmonische Oszillatoren auffast, die Torsionsschwingungen ausfuhren und deren Amplitude temperaturabhangig ist. Dabei ist zu bedenken, das der Quadrupolkern uber den elektrischen Feldgradienten der homoopolaren Bindungselektronen energetisch mit dem ubrigen Molekul gekoppelt ist. Durch diese Kopplung lassen sich auch die beobachteten kurzen Spin-Gitterrelaxationszeitent
1 erklaren, wenn man die Dichte desFourier-Spektrums der Molekulbewegung im Bereich der Quadrupolresonanzfrequenz berucksichtigt. Theoretisch wird gezeigt, das bei Zugrundelegung der Mesergebnisse sich eine Molekultorsionsfrequenz ergibt, die in gleicher Grosenordnung liegt, wie die durchRaman-Untersuchungen an anderen Molekulkristallen gefundenen Werte. Die theoretisch ermittelten Grenzen fur die Spin-Gitterrelaxationszeitt
1 schliesen den Meswert in sich ein. Experiment und Theorie konnten damit in befriedigende Ubereinstimmung gebracht werden.
435 citations
TL;DR: The effect of internal exchange processes in a molecule on high-resolution nuclear magnetic resonance spectra is investigated in this article, where a Boltzmann equation governing the behavior of the nuclear spin density matrix is derived.
Abstract: The effect of internal‐exchange processes in a molecule on high‐resolution nuclear magnetic resonance spectra is investigated. A Boltzmann equation governing the behavior of the nuclear spin density matrix is derived. This equation is valid for arbitrary coupling strengths and exchange rates. The methods of solving this equation are discussed and, in particular, it is shown that the calculation of the steady‐state (slow‐passage) NMR spectrum can be reduced to the solution of a set of simultaneous linear algebraic equations. Explicit approximation formulas for the slow‐ and fast‐exchange limits are derived and a number of examples discussed in detail.
256 citations
TL;DR: In this paper, the authors derived general theoretical expressions for the nuclear spin-lattice relaxation in crystalline solids arising from the interaction of the nuclear electric quadrupole moment with the crystalline electric field.
212 citations