Role of electron spin dynamics and coupling network in designing dynamic nuclear polarization

Equbal, Asif; Jain, Sheetal Kumar; Tagami, Kan; Wang, Xiaoling; Han, Songi

doi:10.1016/j.pnmrs.2021.05.003

Cited by 16 publications

(16 citation statements)

References 88 publications

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“…(23) Note that the buildup rate ω CE [Eq. ( 29)] derived here is similar to those shown in the literature, 12,34,35,38 except on the significance of ΔBzx 3,38,39 in mediating DNP, and that the CE buildup curve should also exhibit a familiar transient oscillation just like other polarization-transfer sequences discussed earlier. We emphasize that the description refers only to the static case.…”

Section: Articlesupporting

confidence: 84%

“…Additionally, it was reported that a high |J/dee| ratio would also help maintain a large adiabaticity of the electron-electron rotor event, which helped maintain a large difference in electron polarization for efficient DNP. 38,40,57 Nevertheless, the |J/dee| ratio cannot be increased indefinitely, or else it might have a deleterious effect. For instance, the simplified CE condition ω 0I ∼ ±Δω is no longer applicable for the strong J case, and the full CE matching condition ω 0I = ± √ (2J + d) 2 + Δω 2 [Eq.…”

Section: The Effect Of J D and δBzx On The Ce-dnp Enhancementmentioning

confidence: 99%

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A unified description for polarization-transfer mechanisms in magnetic resonance in static solids: Cross polarization and DNP

Pang

Jain

Chen

et al. 2022

The Journal of Chemical Physics

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Polarization transfers are crucial building blocks in magnetic resonance experiments, i.e., they can be used to polarize insensitive nuclei and correlate nuclear spins in multidimensional NMR spectroscopy. The polarization can be transferred either across different nuclear spin species or from electron spins to the relatively low-polarized nuclear spins. The former route occurring in solid-state NMR (ssNMR) can be performed via cross polarization (CP), while the latter route is known as dynamic nuclear polarization (DNP). Despite having different operating conditions, we opinionate that both mechanisms are theoretically similar processes in ideal conditions, i.e., the electron is merely another spin-1/2 particle with a much higher gyromagnetic ratio. Here, we show that the CP and DNP processes can be described using a unified theory based on average Hamiltonian theory (AHT) combined with fictitious operators. The intuitive and unified approach has allowed new insights on the cross effect (CE) DNP mechanism, leading to better design of DNP polarizing agents and extending the applications beyond just hyperpolarization. We explore the possibility of exploiting theoretically predicted DNP transients for electron-nucleus distance measurements-like routine dipolar-recoupling experiments in solid-state NMR.

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Section: Articlesupporting

confidence: 84%

Section: The Effect Of J D and δBzx On The Ce-dnp Enhancementmentioning

confidence: 99%

A unified description for polarization-transfer mechanisms in magnetic resonance in static solids: Cross polarization and DNP

Pang

Jain

Chen

et al. 2022

The Journal of Chemical Physics

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“…We turn to DNP and ELDOR spectroscopy to study the cross-talk between different P1 populations via the 13 C NMR probe frequency or directly via pump probe experiments, respectively. DNP is a widely used technique to enhance the intensity of the nuclear magnetic resonance (NMR) signal, but our interest in DNP stems from its sensitivity to the nature of interacting spins. , A recent DNP study of type-Ib diamond samples by Shimon discussed that the observed truncated cross effect can be explained by the existence of coupled P1 spins in the sample in addition to the isolated P1 center, but the fundamental properties of the coupling, whether they are driven by dipolar or exchange coupling, whether there is cross-talk between the different P1 populations, the population of clustered P1 centers, and the mechanistic origin of the proposed Overhauser DNP effect remained unknown. , …”

Section: Introductionmentioning

confidence: 99%

P1 Center Electron Spin Clusters Are Prevalent in Type Ib Diamonds

Bussandri,

Shimon,

Equbal

et al. 2023

J. Am. Chem. Soc.

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Understanding the spatial distribution of the P1 centers is crucial for diamond-based sensors and quantum devices. P1 centers serve as polarization sources for dynamic nuclear polarization (DNP) quantum sensing and play a significant role in the relaxation of nitrogen vacancy (NV) centers. Additionally, the distribution of NV centers correlates with the distribution of P1 centers, as NV centers are formed through the conversion of P1 centers. We utilized DNP and pulsed electron paramagnetic resonance (EPR) techniques that revealed strong clustering of a significant population of P1 centers that exhibit exchange coupling and produce asymmetric line shapes. The 13 C DNP frequency profile at a high magnetic field revealed a pattern that requires an asymmetric EPR line shape of the P1 clusters with electron−electron (e−e) coupling strengths exceeding the 13 C nuclear Larmor frequency. EPR and DNP characterization at high magnetic fields was necessary to resolve energy contributions from different e−e couplings. We employed a two-frequency pump−probe pulsed electron double resonance technique to show cross-talk between the isolated and clustered P1 centers. This finding implies that the clustered P1 centers affect all of the P1 populations. Direct observation of clustered P1 centers and their asymmetric line shape offers a novel and crucial insight into understanding magnetic noise sources for quantum information applications of diamonds and for designing diamond-based polarizing agents with optimized DNP efficiency for 13 C and other nuclear spins of analytes. We propose that room temperature 13 C DNP at a high field, achievable through straightforward modifications to existing solution-state NMR systems, is a potent tool for evaluating and controlling diamond defects.

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“…Recently, materials for high electron spin polarization have attracted much attention for a variety of applications such as dynamic nuclear polarization (DNP), − quantum sensing, and quantum information science . The transfer of enhanced polarization of electron spins to nuclear spins leads to significant increase in the enhancement factor of DNP.…”

Section: Introductionmentioning

confidence: 99%

Dynamic Electron Polarization Lasting More Than 10 μs by Hybridizing Porphyrin and TEMPO with Flexible Linkers

et al. 2023

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Dynamic electron polarization (DEP), induced by quenching of photoexcited species by stable radicals, can hyperpolarize electron spins in solution at room temperature. Recently, development of technologies based on electron spin polarization such as dynamic nuclear polarization (DNP) has been progressing, where it is important to design molecules that achieve long-lasting DEP in addition to high DEP. Hybridization by linking dyes and radicals is a promising approach for efficient DEP, but strong interactions between neighboring dyes and radicals often result in the rapid decay of DEP. In this study, we introduce a flexible linker into the hybrid system of porphyrin and TEMPO to achieve both efficient DEP and long-lasting DEP. The structural flexibility of the linker switches the interaction between the radical and the triplet, which promotes the DEP process by bringing the radical and the triplet into close proximity, while avoiding abrupt relaxation due to strong interactions. As a result, the new hybridized system exhibits a larger DEP than the unlinked system, while at the same time achieving a DEP lasting more than 10 μs.

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Role of electron spin dynamics and coupling network in designing dynamic nuclear polarization

Cited by 16 publications

References 88 publications

A unified description for polarization-transfer mechanisms in magnetic resonance in static solids: Cross polarization and DNP

A unified description for polarization-transfer mechanisms in magnetic resonance in static solids: Cross polarization and DNP

P1 Center Electron Spin Clusters Are Prevalent in Type Ib Diamonds

Dynamic Electron Polarization Lasting More Than 10 μs by Hybridizing Porphyrin and TEMPO with Flexible Linkers

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