Parallel-Mode EPR of Atomic Hydrogen Encapsulated in POSS Cages

Mitrikas, George; Sanakis, Yiannis; Ioannidis, Nikolaos

doi:10.1007/s00723-020-01263-5

Cited by 6 publications

(7 citation statements)

References 36 publications

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“…The hyperfine coupling constant A of the encapsulated D atom is slightly larger than that of H as can be seen from the ratios f = A / A vac , where A vac = 1420.4057 and 218.2562 MHz are the vacuum coupling constants of hydrogen and deuterium, respectively. This result is in line with previous studies and has been attributed to both static and dynamic effects. , The parameters of Table are in very good agreement with those obtained in a recent dual-mode EPR study …”

Section: Resultssupporting

confidence: 92%

“…12,13 The parameters of Table 1 are in very good agreement with those obtained in a recent dual-mode EPR study. 25 The spin−lattice relaxation time, T 1 , is very sensitive to magnetic impurities, and under aerobic conditions a short value of 1 μs is measured at room temperature. To avoid relaxation enhancement effects from paramagnetic oxygen, the EPR quartz tube was filled with helium gas with the method described previously.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Electron Spin Relaxation Mechanisms of Atomic Hydrogen Trapped in Silsesquioxane Cages: The Role of Isotope Substitution

Mitrikas

Carmieli

2021

J. Phys. Chem. C

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Encapsulated atomic hydrogen in silsesquioxane cages is a promising candidate for applications in emerging technologies like spin-based quantum computing, magnetic field sensing, and atomic clock devices. Previous studies on different polyhedral octasilsesquioxanes (POSS) of the type Si8O12R8 have shown that key parameters for quantum computing like electron spin relaxation times T 1 and T M depend strongly on the type of peripheral organic substituents. Herein we examine for the first time the effect of deuterium isotopic substitution on the spin relaxation properties of H@h 72Q8M8, the derivative with R = OSi(CH3)3, by applying pulsed electron paramagnetic resonance (EPR) methods on its deuterated analogues H@d 72Q8M8 and D@d 72Q8M8. For the latter species we measure a phase memory time of 60 μs at 190 K, the largest obtained so far for this family of molecular spins. We show that substitution of peripheral hydrogen atoms with deuterium reveals high-temperature relaxation mechanisms that were previously hidden by proton nuclear spin diffusion. Unusually short T M values observed for all deuterated species even at liquid helium temperatures are discussed in terms of tunneling reorientation of methyl groups.

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Section: Resultssupporting

confidence: 92%

Section: ■ Results and Discussionmentioning

confidence: 99%

Electron Spin Relaxation Mechanisms of Atomic Hydrogen Trapped in Silsesquioxane Cages: The Role of Isotope Substitution

Mitrikas

Carmieli

2021

J. Phys. Chem. C

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“…Weil initially predicted the allowed transitions for the S = 1/2, I = 1/2 hydrogen atom (aiso = 1420 MHz), along with their intensities. 25 Later, Mitrikas et al 27 directly measured both the perpendicular and parallel-mode EPR spectra of the H atom encapsulated in polyhedral oligomeric silsesquioxane cages ( 1 H@h72Q8M8) and observed a hyperfine coupling of A = 1416.58 MHz, in excellent agreement with Weil's proposal. The parallel-mode EPR of the H atom is fairly weak and it is noted that the intensity of both the perpendicular and parallel-mode EPR transitions are determined by the time dependent perturbation solution of the magnetic dipole transition spin-Hamiltonian operator.…”

Section: Introductionsupporting

confidence: 54%

“…More simply stated, the intensity of the parallel-mode EPR is proportional to the degree of state-mixing, which is greatest in the low field regime. Mitrikas et al 27 recognized the potential of parallel-mode EPR spectroscopy to other S = 1/2 systems and reported the predicted perpendicular and parallel-mode EPR spectra of Bi:Si.…”

Section: Introductionmentioning

confidence: 99%

X-band Parallel-Mode and Multifrequency Electron Paramagnetic Resonance Spectroscopy of S = 1/2 Bismuth Centers

Haak

Krüger

Abrosimov

et al. 2022

Preprint

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The recent successes in the isolation and characterization of several bismuth radicals inspire the development of new spectroscopic approaches for the in-depth analysis of their electronic structure. Electron paramagnetic resonance (EPR) spectroscopy is a powerful tool for the characterization of main group radicals. However, the large electron-nuclear hyperfine interactions of Bi (209Bi, I = 9/2) have presented difficult challenges to fully interpret the spectral properties for some of these radicals. Parallel-mode EPR (B1 || B0) is almost exclusively employed for the study of S > 1/2 systems but becomes feasible for S = 1/2 systems with large hyperfine couplings, offering a distinct EPR spectroscopic method. Herein, we demonstrate the application of conventional X-band parallel-mode EPR for S = 1/2, I = 9/2 spin systems: Bi doped crystalline silicon (Bi:Si) and the molecular Bi radicals: [L(X)Ga]2Bi• (X = Cl, I) and [L(Cl)GaBi(MecAAC)]• (L = HC[MeCN(2,6-iPr2C6H3)]2). In combination with multifrequency perpendicular-mode EPR (X-, Q-, and W-band frequency), we were able to fully refine both of the anisotropic g- and A-tensors of these molecular radicals. The parallel-mode EPR experiments demonstrated and discussed here have the potential to enable the characterization of other S = 1/2 systems with large hyperfine couplings, which is often challenging by conventional perpendicular-mode EPR techniques. Considerations pertaining to the choice of microwave frequency are discussed for relevant spin-systems.

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“…Weil initially predicted the allowed transitions for the S = 1/2, I = 1/2 hydrogen atom ( a iso = 1420 MHz), along with their intensities . Later, Mitrikas et al directly measured both the perpendicular- and parallel-mode EPR spectra of the H atom encapsulated in polyhedral oligomeric silsesquioxane cages ( 1 H@ h 72 Q 8 M 8 ) and observed a hyperfine coupling of A = 1416.58 MHz, in excellent agreement with Weil’s proposal. The parallel-mode EPR of the H atom is fairly weak, and it is noted that the intensity of both the perpendicular- and parallel-mode EPR transitions is determined by the time-dependent perturbation solution of the magnetic dipole transition spin-Hamiltonian operator.…”

Section: Introductionmentioning

confidence: 63%

X-Band Parallel-Mode and Multifrequency Electron Paramagnetic Resonance Spectroscopy of S = 1/2 Bismuth Centers

et al. 2022

View full text Add to dashboard Cite

The recent successes in the isolation and characterization of several bismuth radicals inspire the development of new spectroscopic approaches for the in-depth analysis of their electronic structure. Electron paramagnetic resonance (EPR) spectroscopy is a powerful tool for the characterization of main group radicals. However, the large electron–nuclear hyperfine interactions of Bi ( 209 Bi, I = 9/2) have presented difficult challenges to fully interpret the spectral properties for some of these radicals. Parallel-mode EPR ( B 1 ∥ B 0 ) is almost exclusively employed for the study of S > 1/2 systems but becomes feasible for S = 1/2 systems with large hyperfine couplings, offering a distinct EPR spectroscopic approach. Herein, we demonstrate the application of conventional X-band parallel-mode EPR for S = 1/2, I = 9/2 spin systems: Bi-doped crystalline silicon (Si:Bi) and the molecular Bi radicals [L(X)Ga] 2 Bi • (X = Cl or I) and [L(Cl)GaBi( Me cAAC)] •+ (L = HC[MeCN(2,6- i Pr 2 C 6 H 3 )] 2 ). In combination with multifrequency perpendicular-mode EPR (X-, Q-, and W-band frequencies), we were able to fully refine both the anisotropic g - and A -tensors of these molecular radicals. The parallel-mode EPR experiments demonstrated and discussed here have the potential to enable the characterization of other S = 1/2 systems with large hyperfine couplings, which is often challenging by conventional perpendicular-mode EPR techniques. Considerations pertaining to the choice of microwave frequency are discussed for relevant spin-systems.

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Parallel-Mode EPR of Atomic Hydrogen Encapsulated in POSS Cages

Cited by 6 publications

References 36 publications

Electron Spin Relaxation Mechanisms of Atomic Hydrogen Trapped in Silsesquioxane Cages: The Role of Isotope Substitution

Electron Spin Relaxation Mechanisms of Atomic Hydrogen Trapped in Silsesquioxane Cages: The Role of Isotope Substitution

X-band Parallel-Mode and Multifrequency Electron Paramagnetic Resonance Spectroscopy of S = 1/2 Bismuth Centers

X-Band Parallel-Mode and Multifrequency Electron Paramagnetic Resonance Spectroscopy of S = 1/2 Bismuth Centers

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