Beyond the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>T</mml:mi><mml:mn>1</mml:mn></mml:msub></mml:math>Limit: Singlet Nuclear Spin States in Low Magnetic Fields

Carravetta, Marina; Johannessen, Ole G.; Levitt, Malcolm H.

doi:10.1103/physrevlett.92.153003

Cited by 346 publications

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“…In low magnetic field, the chemical shift anisotropy mechanism is absent, and the intramolecular dipole-dipole coupling does not cause singlet relaxation. [1][2][3][4][5][6][7] In a forthcoming publication we show that for pure spin-rotation relaxation, 12 the ratio of T S and T 1 is given by (6) where C j and C k are the spin-rotation tensors for the two 15 N sites. This equation takes into account the strong cross-correlation of the spin-rotation interactions in this linear molecule.…”

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confidence: 81%

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The Long-Lived Nuclear Singlet State of ¹⁵N-Nitrous Oxide in Solution

et al. 2008

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Nuclear singlet states may have lifetimes T S that exceed the conventional magnetization relaxation time T 1 by an order of magnitude. [1][2][3][4][5][6][7][8][9][10][11] Applications of these states to the NMR measurements of slow molecular diffusion, chemical exchange, and the transportofhyperpolarizednuclearspinorderhavebeendemonstrated. [8][9][10][11] So far, long-lived nuclear singlet states have only been observed for proton pairs. We now demonstrate an extraordinarily long lifetime (T S ) of ∼26 min for the nuclear spin singlet of 15 N 2 -nitrous oxide (dinitrogen monoxide, N 2 O) in solution. This result has high potential importance since nitrous oxide is soluble in many important fluids such as water, oil, and blood. It is used routinely as a food additive, a gas propellant, and an anesthetic.Doubly labeled 15 N 2 O gas, purchased from CK-gas (UK), was dissolved in a degassed solution of DMSO-d 6 at a pressure of ∼3. Figure 1a.The slow relaxation of singlet states is revealed by suppressing their interconversion with the triplet states, either by using a resonant radiofrequency field [3][4][5][6] or by reducing the static magnetic field to a very low value. 1,2 The radiofrequency method is not feasible for The spin system is allowed to reach thermal equilibrium, and two strong 90°pulses with a relative phase of 90°are applied at the mean chemical shift frequency of the two 15 N sites. The delay between the pulses, τ 1 ) 0.198 ms, was chosen so that the transverse magnetization vectors of the two 15 N sites precess through 180°r elative to each other. The two pulses act as a selective 180°pulse on one of the 15 N sites and lead to a spin density operator 10 of the formwhere the two sites are denoted j and k and the selective inversion is assumed to act on site j. In this and the following equations, the subscript refers to a time point in Figure 2. The sample is transported out of the magnetic field by activating a stepper motor to wind up a string attached to the sample holder. The transport process takes τ tr ) 40 s and transports the sample into a region of low magnetic field, B low ≈ 2 mT, estimated by a Hall effect device. As shown in ref 2, slow adiabatic transport converts the population of each high-field state into that of the corresponding low-field state, leading to a density operator of the formwhere the low-field eigenstates areThe sample is left in the low-field region for a variable time τ LF . During the first few minutes, the three triplet populations equilibrate with each other on a time scale set by the relaxation constant T 1 . The density operator after several minutes in low magnetic field is therefore given approximately byThe sample is transported back into the high-field region by running the stepper motor in the opposite direction. Adiabatic transport from the density operator in eq 3 leads to

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“…The fieldcycling procedure shown in Figure 2 was therefore used. This is a modified version of the method used in ref 1.…”

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The Long-Lived Nuclear Singlet State of ¹⁵N-Nitrous Oxide in Solution

et al. 2008

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“…Levitt et al have demonstrated a long living antisymmetric state arrived by shifting the sample from high to very low magnetic field, suggesting that this long living state could be used as memory qubit [31,32]. In such cases fidelity of computation depends on how much the memory qubits have been deviated from the initialized state at the beginning of the computation till the time they are actually used.…”

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Relaxation of pseudo pure states: the role of cross-correlations

Ghosh

Kumar

2005

Journal of Magnetic Resonance

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In Quantum Information Processing by NMR one of the major challenges is relaxation or decoherence. Often it is found that the equilibrium mixed state of a spin system is not suitable as an initial state for computation and a definite initial state is required to be prepared prior to the computation. As these preferred initial states are non-equilibrium states, they are not stationary and are destroyed with time as the spin system relaxes toward its equilibrium, introducing error in computation. Since it is not possible to cut off the relaxation processes completely, attempts are going on to develop alternate strategies like Quantum Error Correction Codes or Noiseless Subsystems. Here we study the relaxation behavior of various Pseudo Pure States and analyze the role of Cross terms between different relaxation processes, known as Cross-correlation. It is found that while cross-correlations accelerate the relaxation of certain pseudo pure states, they retard that of others.

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“…However, in 2004 Levitt and co‐workers showed that it was possible to create analogous non‐magnetic singlet states more generally between pairs of spin‐1/2 nuclei that are magnetically inequivalent and have lifetimes that are much longer than T 1 18. Consequently, the spin–lattice relaxation time constant T 1 is no longer the time‐limiting barrier for nuclear spin memory and such long‐lived singlet states (LLS) reflect an important and rapidly developing area of NMR spectroscopy 19, 20, 21, 22.…”

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A Hyperpolarizable ¹H Magnetic Resonance Probe for Signal Detection 15 Minutes after Spin Polarization Storage

et al. 2016

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Nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) are two extremely important techniques with applications ranging from molecular structure determination to human imaging. However, in many cases the applicability of NMR and MRI are limited by inherently poor sensitivity and insufficient nuclear spin lifetime. Here we demonstrate a cost‐efficient and fast technique that tackles both issues simultaneously. We use the signal amplification by reversible exchange (SABRE) technique to hyperpolarize the target 1H nuclei and store this polarization in long‐lived singlet (LLS) form after suitable radiofrequency (rf) pulses. Compared to the normal scenario, we achieve three orders of signal enhancement and one order of lifetime extension, leading to 1H NMR signal detection 15 minutes after the creation of the detected states. The creation of such hyperpolarized long‐lived polarization reflects an important step forward in the pipeline to see such agents used as clinical probes of disease.

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Beyond theT1Limit: Singlet Nuclear Spin States in Low Magnetic Fields

Cited by 346 publications

References 20 publications

The Long-Lived Nuclear Singlet State of ¹⁵N-Nitrous Oxide in Solution

The Long-Lived Nuclear Singlet State of ¹⁵N-Nitrous Oxide in Solution

Relaxation of pseudo pure states: the role of cross-correlations

A Hyperpolarizable ¹H Magnetic Resonance Probe for Signal Detection 15 Minutes after Spin Polarization Storage

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Beyond theT1Limit: Singlet Nuclear Spin States in Low Magnetic Fields

Cited by 346 publications

References 20 publications

The Long-Lived Nuclear Singlet State of 15N-Nitrous Oxide in Solution

The Long-Lived Nuclear Singlet State of 15N-Nitrous Oxide in Solution

Relaxation of pseudo pure states: the role of cross-correlations

A Hyperpolarizable 1H Magnetic Resonance Probe for Signal Detection 15 Minutes after Spin Polarization Storage

Contact Info

Product

Resources

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The Long-Lived Nuclear Singlet State of ¹⁵N-Nitrous Oxide in Solution

The Long-Lived Nuclear Singlet State of ¹⁵N-Nitrous Oxide in Solution

A Hyperpolarizable ¹H Magnetic Resonance Probe for Signal Detection 15 Minutes after Spin Polarization Storage