Dynamic nuclear polarization with trityl radicals

Palani, Ravi Shankar; Mardini, Michael; Quan, Yifan; Griffin, Robert G.

doi:10.1016/j.jmr.2023.107411

Cited by 15 publications

(13 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It results in a dispersive DNP field profile when microwave irradiation is applied near the EPR resonance, hence the name. The Zeeman field profile is similar to that observed for TM, and we believe RM explains the DNP Zeeman field profile of the some recently published trityl data 35,38 .…”

Section: In Addition Tosupporting

confidence: 86%

“…Finally, in a recent paper 35 , we show that even with aggregation of the trityl radicals the electron-electron interaction is not strong enough to induce triple spin flip for TM and the spin temperature of the 13 C is completely decoupled from 1 H. The spin temperatures of 13 C and 1 H can even have different signs with microwave irradiation. This proves that the electron-electron coupling is not strong enough to span the nuclear Larmor frequency of 1 H at 380 MHz so that 1 H and 13 C can reside in the same electron spin bath.…”

Section: Resonant Mixing Differential Contributionsmentioning

confidence: 68%

See 1 more Smart Citation

Resonant Mixing Dynamic Nuclear Polarization

Quan

Ouyang

Mardini

et al. 2023

Preprint

View full text Add to dashboard Cite

We propose a new mechanism for dynamic nuclear polarization that is different from the well-known Overhauser effect, solid effect, cross effect and thermal mixing processes. In particular, we discovered that the evolution of the density matrix with the simple Hamiltonian of a coupled electron-nuclear spin pair with weak microwave irradiation yields a nuclear polarization enhancement when irradiating near the electron Larmor frequency. We denote the mechanism as Resonant Mixing (RM). We believe that this mechanism is responsible for the observed dispersive shaped DNP field profile for trityl samples near the electron paramagnetic resonance center. This new effect is due to mixing of states by the microwave field together with the electron-nuclear coupling, and involves the same interactions as the SE. However, the SE is optimal when the microwave field is off-resonance, whereas RM is optimal when the microwave field is on-resonance.

show abstract

Section: In Addition Tosupporting

confidence: 86%

Section: Resonant Mixing Differential Contributionsmentioning

confidence: 68%

Resonant Mixing Dynamic Nuclear Polarization

Quan

Ouyang

Mardini

et al. 2023

Preprint

View full text Add to dashboard Cite

show abstract

“…The Zeeman field profile is similar to that observed for TM, and we believe that RM explains the DNP Zeeman field profile of some recently published trityl data. 40,42 RM is induced by the microwave and the hyperfine interaction, just as for the SE. However, SE transitions occur when the microwave field is off-resonance at ω 0S ± ω 0I .…”

Section: P T I T I T ( )mentioning

confidence: 99%

“…Karabanov et al 37 observed a well-resolved dispersive profile near the EPR center with a trityl concentration of only 15 mM; that this profile appears under these conditions further suggests that the mechanism at play is not TM and probably is an effect involving a single electron spin interacting with surrounding nuclear spins. We have also looked for direct evidence of TM in a trityl system, 40 but we found that even with aggregation of the trityl radicals, the electron−electron interaction is not strong enough to induce three-spin flips involved in TM and that the spin temperature of the 13 C is completely decoupled from 1 H. The spin temperatures of 13 C and 1 H can even have different signs with microwave irradiation, completely contrary to the conceptual picture of TM. 40 In order to rationalize these observations and the dispersive Zeeman DNP field profile, we propose a new mechanism termed resonance mixing (RM).…”

mentioning

confidence: 97%

“…We have also looked for direct evidence of TM in a trityl system, 40 but we found that even with aggregation of the trityl radicals, the electron−electron interaction is not strong enough to induce three-spin flips involved in TM and that the spin temperature of the 13 C is completely decoupled from 1 H. The spin temperatures of 13 C and 1 H can even have different signs with microwave irradiation, completely contrary to the conceptual picture of TM. 40 In order to rationalize these observations and the dispersive Zeeman DNP field profile, we propose a new mechanism termed resonance mixing (RM). We first present additional experimental profiles illustrating the effect, acquired under conditions under which we argue TM should not be present.…”

mentioning

confidence: 97%

See 1 more Smart Citation

Resonant Mixing Dynamic Nuclear Polarization

Quan,

Ouyang,

Mardini

et al. 2023

J. Phys. Chem. Lett.

Self Cite

View full text Add to dashboard Cite

We propose a mechanism for dynamic nuclear polarization that is different from the well-known Overhauser effect, solid effect, cross effect, and thermal mixing processes. We term it Resonant Mixing (RM), and we show that it arises from the evolution of the density matrix for a simple electron–nucleus coupled spin pair subject to weak microwave irradiation, the same interactions as the solid effect. However, the SE is optimal when the microwave field is off-resonance, whereas RM is optimal when the microwave field is on-resonance and involves the mixing of states by the microwave field together with the electron–nuclear coupling. Finally, we argue that this mechanism is responsible for the observed dispersive-shaped DNP field profile for trityl samples near the electron paramagnetic resonance center.

show abstract