Correlation between EPR spectra and coloration of natural diamonds

Lee, Charis W.Y.; Cheng, Juan; Yiu, YM; Chan, K.‐C.; Lau, Dominique; Tang, Weiyue; Cheng, Ke; Kong, Tom C.; Hui, Tony K.C.; Jelezko, Fedor

doi:10.1016/j.diamond.2020.107728

Cited by 8 publications

(15 citation statements)

References 10 publications

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“…It manifests itself as a broad signal underneath the characteristic P1 center EPR spectrum and is thus hard to detect and identify by using conventional low-field CW EPR techniques. This population is distinct from the exchange-coupled P1 pairs that give rise to an EPR signal with resolved sharp lines in between the 14 N hyperfine lines in high-power CW EPR experiments. − …”

Section: Introductionmentioning

confidence: 94%

Nitrogen Substitutions Aggregation and Clustering in Diamonds as Revealed by High-Field Electron Paramagnetic Resonance

Nir-Arad,

Shlomi,

Manukovsky

et al. 2023

J. Am. Chem. Soc.

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Diamonds have been shown to be an excellent platform for quantum computing and quantum sensing applications. These applications are enabled by the presence of defects in the lattice, which are also known as color centers. The most common nitrogen-based defect in synthetic diamonds is the paramagnetic nitrogen substitution (P1) center. While the majority of quantum applications rely on nitrogen-vacancy (NV) centers, the properties of the latter are heavily influenced by the presence and the spatial distribution of the P1 centers. Hence, understanding the spatial distribution and mutual interactions of P1 centers is crucial for the successful development of diamond-based quantum devices. Unlike NV centers, P1 centers do not have a spin-dependent optical signature, and their spin-related properties, therefore, have to be detected and characterized using magnetic resonance methods. We show that using high-field (6.9 and 13.8 T) pulsed electron paramagnetic resonance (EPR) and dynamic nuclear polarization (DNP) experiments, we can distinguish and quantify three distinct populations of P1 centers: isolated P1 centers, weakly interacting ones, and exchange-coupled ones that are clustered together. While such clustering was suggested before, these clusters were never detected directly and unambiguously. Moreover, by using electron−electron double resonance (ELDOR) pump−probe experiments, we demonstrate that the latter clustered population does not exist in isolation but coexists with the more weakly interacting P1 centers throughout the diamond lattice. Its presence thus strongly affects the quantum properties of the diamond. We also show that the existence of this population can explain recent hyperpolarization results in type Ib high-pressure, high-temperature (HPHT) diamonds. We propose a combination of high-field pulsed EPR, ELDOR, and DNP as a tool for probing the aggregation state and interactions among different populations of nitrogen substitution centers.

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Section: Introductionmentioning

confidence: 94%

Nitrogen Substitutions Aggregation and Clustering in Diamonds as Revealed by High-Field Electron Paramagnetic Resonance

Nir-Arad,

Shlomi,

Manukovsky

et al. 2023

J. Am. Chem. Soc.

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“…In the diamond crystal, there is a very low concentration (<10 −5 M) of carbon-centered paramagnetic centers (stable carbon radicals). These paramagnetic centers can be evaluated using EPR (Electron Paramagnetic Resonance) spectroscopy [22][23][24][25]. In EPR, when a radical (defined as an atom with an unpaired electron) under a magnetic field is exposed to microwave radiation, it will subvert from its equilibrium state and will orient in a direction parallel or antiparallel to the direction of the magnetic field.…”

Section: Uv Pl Eprmentioning

confidence: 99%

“…Table 2 presents different types of paramagnetic centers (defects) that have been reported and are correlated with type Ia diamonds and/or treated diamonds (irradiated or thermally treated) [27][28][29][30]. In some cases, a correlation between the EPR center and the optical center is observed, e.g., P2 and the optical center N3, which results in some diamonds having a yellow color [23,25,31]. The research hypothesis was that EPR spectroscopy can be used to determine the correlation between stable carbon-centered radicals in N-contaminated diamonds and the structure of the nitrogen atoms and their color for the following reasons:…”

Section: Uv Pl Eprmentioning

confidence: 99%

Nitrogen Structure Determination in Treated Fancy Diamonds via EPR Spectroscopy

Litvak

Cahana²,

Anker

et al. 2022

Crystals

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Color induction in nitrogen-contaminated diamonds was carried out via various procedures that involve irradiation, thermal treatments (annealing), and more. These treatments affect vacancy defect production and atom orientation centers in the diamond lattice. Natural diamonds underwent color enhancement treatments in order to produce green, blue, and yellow fancy diamonds. The aim of this study was to follow the changes occurring during the treatment, mainly by EPR spectroscopy, which is the main source for the determination of the effect of paramagnetic centers (carbon-centered radicals) on the color centers produced via the treatments, but also via visual assessment, fluorescence, UV-vis, and FTIR spectroscopy. The results indicate that diamonds containing high levels of nitrogen contamination are associated with high carbon-centered radical concentrations. Four paramagnetic center structures (N1, N4, and P2/W21) were generated by the treatment. It is suggested that the N4 structure correlates with the formation of blue color centers, whereas yellow color centers are attributed to the presence of N1 species. While to produce blue and yellow colors, a thermal treatment is needed after irradiation, for treated green diamonds, no thermal treatment is needed (only irradiation).

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“…By evaluating g -values (corresponding to the fingerprints of paramagnetic centers) and hyperfine values (reflecting interactions between paramagnetic centers and nearby magnetic nuclei), information on a paramagnetic center and its nearby environment can be obtained. 10 For example, it was shown that Ib diamonds display a P1 paramagnetic defect with a specific hyperfine structure (A) that is related to the 14 N nuclear spin I = 1, with a natural abundance of 99.6%. 8 Diamonds categorized as B-center by IR spectroscopy present a P2 paramagnetic center after high-temperature annealing treatment.…”

Section: Introductionmentioning

confidence: 99%