Double Resonance Research Articles

On the steady-state interfacial waves with two-dimensional type-A double exact resonance

Steady-state interfacial waves under two-dimensional (2D) type-A exact triad resonance and other related resonances are researched in a two-layer liquid model with a free surface in contact with air. Five groups (groups 1–5) of convergent series solutions are achieved via the homotopy analysis method. It is found that the phenomenon of double exact resonance could exist in periodic interfacial waves if physical parameters correspond to the intersection of two exact resonance curves. The double exact resonance considered here contains a 2D type-A triad resonance and an other resonance. Under the 2D type-A exact triad resonance, the other resonant triad could obviously enlarge or reduce the wave amplitudes and energy proportions of primary and resonant components. Nevertheless, other resonant quartet, quintet, sextet, and septet all produce no influence on interfacial waves when the 2D type-A exact triad resonance occurs. The above-mentioned results indicate that in the neighborhood of the double exact triad resonance, small perturbations of wave vector of a primary component can cause huge changes on wave profiles of free surface and interface, wave amplitude spectrum, and energy distribution of internal waves in real ocean. In addition, the closer the interfacial waves are to the double exact triad resonance, the more possible energy combinations exist in the wave system, and the greater the number of steady-state interfacial wave solutions. All of this should deepen our understanding of nonlinear resonance interactions in short-crested internal waves.

Optical pressure sensor based on Fano resonance in a coupled resonator system

Optical pressure sensor plays a very important role in micro deformation detection, environmental monitoring, and medical fields. However, the quantitative relationship between the applied pressure and the optical response of the resonator before and after deformation is difficult to obtain. In this paper, a coupled resonator system based on metal-insulator-metal waveguide for optical pressure sensor is proposed. The mechanical properties of the system and the optical transmission properties before and after applied pressure are analyzed in detail by using the finite element method. Simulation results show that the maximum deformation of the resonator has a simple linear relationship with the applied pressure. We give a direct definition of the sensitivity of the optical pressure sensor. And based on the Fano resonance phenomenon caused by the coupling the slot cavity with the groove cavity, the optical pressure sensor with a sensitivity of 6.75 nm/MPa is achieved. In addition, we add stub resonator to obtain double Fano resonance phenomenon, and with the change of external pressure, the two Fano line types show different change laws. Specifically, a suitable pressure value can make a double Fano resonance become a single Fano resonance. The special features of our suggested structure are applicable to detecting optical property changes under different pressures, chemical high pressure experimental measurement and study of chemical reaction kinetics process.

Experimental investigation of an Autler-Townes resonator with flow

The acoustic behavior of a double annular resonator with flow is studied as a special case to illustrate the possibilities, but also the difficulties, offered by flow on the acoustic performance of metamaterials. Compared with the associated single resonator, the double resonator exhibits – in the lossless case – a transmission peak near the resonant frequency. This peak is associated with an evanescent out-of-phase coupling between the two resonators and is known in literature as “Autler-Townes splitting”. In measurements with a double resonator, this peak is strongly attenuated by viscous effects, to such an extent that it almost disappears. When a flow is added, even a very small one, a gain is created and the peak reappears close to the resonator frequency. As the average flow velocity increases, this gain can become sufficiently large for a whistling to appear.

Determining and controlling conformational information from orientationally selective light-induced triplet-triplet electron resonance spectroscopy for a set of bis-porphyrin rulers.

We recently reported a new technique, light-induced triplet-triplet electron resonance (LITTER) spectroscopy, which allows quantification of the dipolar interaction between the photogenerated triplet states of two chromophores. Here we carry out a systematic LITTER study, considering orientation selection by the detection pulses, of a series of bis-porphyrin model peptides with different porphyrin-porphyrin distances and relative orientations. Orientation-dependent analysis of the dipolar datasets yields conformational information of the molecules in frozen solution which is in good agreement with density functional theory predictions. Additionally, a fast partial orientational-averaging treatment produces distance distributions with minimized orientational artefacts. Finally, by direct comparison of LITTER data to double electron-electron resonance (DEER) measured on a system with Cu(II) coordinated into the porphyrins, we demonstrate the advantages of the LITTER technique over the standard DEER methodology. This is due to the remarkable spectroscopic properties of the photogenerated porphyrin triplet state. This work sets the basis for the use of LITTER in structural investigations of unmodified complex biological macromolecules, which could be combined with Förster resonance energy transfer and microscopy inside cells.

Particle-in-cell simulations of electron–positron cyclotron maser forming pulsar radio zebras

Context. The microwave radio dynamic spectra of the Crab pulsar interpulse contain fine structures represented via narrowband quasiharmonic stripes. The pattern significantly constrains any potential emission mechanism. Similar to the zebra patterns observed, for example, in type IV solar radio bursts or decameter and kilometer Jupiter radio emission, the double plasma resonance (DPR) effect of the cyclotron maser instability may allow for interpretion of observations of pulsar radio zebras. Aims. We provide insight at kinetic microscales of the zebra structures in pulsar radio emissions originating close to or beyond the light cylinder. Methods. We present electromagnetic relativistic particle-in-cell (PIC) simulations of the electron–positron cyclotron maser for cyclotron frequency smaller than the plasma frequency. In four distinct simulation cycles, we focused on the effects of varying the plasma parameters on the instability growth rate and saturation energy. The physical parameters were the ratio between the plasma and cyclotron frequency, the density ratio of the “hot” loss-cone to the “cold” background plasma, the loss-cone characteristic velocity, and comparison with electron–proton plasma. Results. In contrast to the results obtained from electron–proton plasma simulations (for example, in solar system plasmas), we find that the pulsar electron–positron maser instability does not generate distinguishable X and Z modes. On the contrary, a singular electromagnetic XZ mode was generated in all studied configurations close to or above the plasma frequency. The highest instability growth rates were obtained for the simulations with integer plasma-to-cyclotron frequency ratios. The instability is most efficient for plasma with characteristic loss-cone velocity in the range vth = 0.2 − 0.3c. For low density ratios, the highest peak of the XZ mode is at double the frequency of the highest peak of the Bernstein modes, indicating that the radio emission is produced by a coalescence of two Bernstein modes with the same frequency and opposite wave numbers. Our estimate of the radiative flux generated from the simulation is up to ∼30 mJy from an area of 100 km2 for an observer at 1 kpc distance without the inclusion of relativistic beaming effects, which may account for multiple orders of magnitude.

Structural Flexibility of Tau in Its Interaction with Microtubules as Viewed by Site-Directed Spin Labeling EPR Spectroscopy.

Tau is a microtubule-associated protein that belongs to the Intrinsically Disordered Proteins (IDPs) family. IDPs or Intrinsically Disordered Regions (IDRs) play key roles in protein interaction networks and their dysfunctions are often related to severe diseases. Defined by their lack of stable secondary and tertiary structures in physiological conditions while being functional, these proteins use their inherent structural flexibility to adapt to and interact with various binding partners. Knowledges on the structural dynamics of IDPs and their different conformers are crucial to finely decipher fundamental biological processes controlled by mechanisms such as conformational adaptations or switches, induced fit, or conformational selection events. Different mechanisms of binding have been proposed: among them, the so-called folding-upon-binding in which the IDP adopts a certain conformation upon interacting with a partner protein, or the formation of a "fuzzy" complex in which the IDP partly keeps its dynamical character at the surface of its partner. The dynamical nature and physicochemical properties of unbound as well as bound IDPs make this class of proteins particularly difficult to characterize by classical bio-structural techniques and require specific approaches for the fine description of their inherent dynamics.Among other techniques, Site-Directed Spin Labeling combined with Electron Paramagnetic Resonance (SDSL-EPR) spectroscopy has gained much interest in this last decade for the study of IDPs. SDSL-EPR consists in grafting a paramagnetic label (mainly a nitroxide radical) at selected site(s) of the macromolecule under interest followed by its observation using and/or combining different EPR strategies. These nitroxide spin labels detected by continuous wave (cw) EPR spectroscopy are used as perfect reporters or "spy spins" of their local environment, being able to reveal structural transitions, folding/unfolding events, etc. Another approach is based on the measurement of inter-label distance distributions in the 1.5-8.0nm range using pulsed dipolar EPR experiments, such as Double Electron-Electron Resonance (DEER) spectroscopy. The technique is then particularly well suited to study the behavior of Tau in its interaction with its physiological partner: microtubules (MTs). In this chapter we provide a detailed experimental protocol for the labeling of Tau protein and its EPR study while interacting with preformed (Paclitaxel-stabilized) MTs, or using Tau as MT inducer. We show how the choice of nitroxide label can be crucial to obtain functional information on Tau/tubulin complexes.

Plasmon-enhanced second harmonic generation of metal nanostructures.

As the most common nonlinear optical process, second harmonic generation (SHG) has important application value in the field of nanophotonics. With the rapid development of metal nanomaterial processing and chemical preparation technology, various structures based on metal nanoparticles have been used to achieve the enhancement and modulation of SHG. In the field of nonlinear optics, plasmonic metal nanostructures have become potential candidates for nonlinear optoelectronic devices because of their highly adjustable physical characteristics. In this article, first, the basic optical principles of SHG and the source of surface symmetry breaking in metal nanoparticles are briefly introduced. Next, the related reports on SHG in metal nanostructures are reviewed from three aspects: the enhancement of SHG efficiency by double resonance structures, the SHG effect based on magnetic resonance and the harmonic energy transfer. Then, the applications of SHG in the sensing, imaging and in situ monitoring of metal nanostructures are summarized. Future opportunities for SHG in composite systems composed of metal nanostructures and two-dimensional materials are also proposed.

Double-order coupling bandgap design of metamaterial beams and broadband vibration reduction properties

<sec>Local-resonance bandgap and Bragg bandgap can coexist in a metamaterial beam, and their coupling effect can be used to realize ultra-wide bandgap, which has great potential applications in the field of wide-band vibration reduction. Previous studies usually considered the single-order coupling between the local-resonance bandgap and Bragg bandgap in metamaterial beams with a single array of local resonators, which can only achieve the single-order ultra-wide coupling bandgap and cannot meet the wide-band vibration reduction requirements of double/multiple target frequency bands. In this paper, metamaterial beams with double arrays of local resonators are considered, and the regulation design and analysis of double-order coupling of local-resonance and Bragg bandgaps are carried out based on an analytical model of bending wave dispersion relation. Moreover, the vibration reduction characteristics of the double-frequency-resonator metamaterial beams with double-order coupling bandgaps are studied by using spectral element method and the finite element method. The main conclusions are as follows.</sec><sec>1) A design method is proposed for realizing double-order coupling wide bandgap in a metamaterial beam with double arrays of local resonators. By using this method, the resonance frequencies of the local resonators can be quickly designed on conditions that host beam parameters, lattice constant and added mass ratio of the local resonators are given.</sec><sec>2) The double-order coupling bandgaps in a metamaterial beam carrying double arrays of local resonators are compared with the single-order coupling bandgaps in metamaterial beams with a single array of local resonators. It is found that through proper design, the total normalized width of the double-order coupling bandgap can be much broader than that of the single-order coupling bandgap, so the double-order coupling bandgap is more beneficial to wide-band vibration reduction.</sec><sec>3) It is found that for a given total added mass ratio of the double arrays of local resonators, it is necessary to optimize the mass distribution ratio of the double resonators to maximize the total normalized width of double-order coupling bandgap. An approximate formula for designing the optimal mass distribution ratio of the double resonators is further established.</sec><sec>4) The spectral element method is used to study the vibration reduction characteristics of the metamaterial beams carrying double arrays of local resonators designed based on double-order bandgap coupling. The accuracy of the spectral element method is verified by comparing with the finite element method. The results show that significant vibration reduction can be achieved in two wide frequency bands corresponding to the double-order coupling bandgaps. The influences of number of unit cells and resonator damping on the vibration reduction characteristics of the metamaterial beam are further analyzed. It is shown that the increase of number of unit cells can enhance the vibration reduction performance in the bandgap, and the increase of resonator damping can effectively broaden the vibration reduction frequency band.</sec>

Enhanced double resonance Raman scattering in multilayer graphene with broadband coherent anti-Stokes Raman spectroscopy.

Graphene's unique gapless band structure and remarkably large third-order optical susceptibility have drawn significant attention to its nonlinear optical response, particularly in the context of coherent anti-Stokes Raman scattering (CARS). Under the combined influence of phononic and electronic resonances, the CARS response of graphene has been observed to exhibit a distinctive feature of time-resolved dip-to-peak evolution. Here, we report a greatly enhanced double resonance Raman mode beyond the G mode of multi-layer graphene with broadband CARS measurements. The significant difference in the intensity ratio between CARS and SR for this mode may be attributed to the preferential activation of low-frequency phonons in the impulsive stimulated Raman scattering process (ISRS) and a lower dephasing rate. Our results build on a foundation towards a deeper exploration of the coherent Raman response of two-dimensional materials.

Conformational Heterogeneity of β-Barrel Membrane Proteins Observed In Situ Using Orthogonal Spin Labels and Pulsed ESR Spectroscopy.

Outer membrane proteins (OMPs) of Gram-negative bacteria are involved in many essential functions of the cell. They are tightly packed in the outer membrane, which is an asymmetric lipid bilayer. Electron spin resonance (ESR) spectroscopic techniques combined with site-directed spin labeling (SDSL) enable observation of structure and conformational dynamics of these proteins directly in their native environments. Here we depict a protocol for site-directed spin labeling of β-barrel membrane proteins in isolated outer membranes and intact E. coli using nitroxide, triarylmethyl (trityl), and Gd3+-based spin tags. Furthermore, subsequent continuous wave (CW) and orthogonal pulsed electron-electron double resonance (PELDOR) measurements are described along with experimental setup at Q-band (34GHz), the data analysis, and interpretation.

On the peculiar EPR spectra of P1 centers at high (12-20 T) magnetic fields.

The most common lattice defect in high-pressure high-temperature (HPHT) diamonds is the nitrogen substitution (P1) center. This is a paramagnetic defect with a single unpaired electron spin coupled to a 14N nuclear spin forming an S = 1/2, I = 1 spin system. While P1 centers have been studied by electron paramagnetic resonance (EPR) spectroscopy for decades, only recently did their behavior at ultra-high (>12 T) magnetic fields become of interest. This is because P1 centers were recently found to be very efficient polarizing agents in dynamic nuclear polarization (DNP) experiments, which are typically carried out at high magnetic fields. The P1 ultra-high field EPR spectra show multiple peaks which the lower fields spectra do not. In this paper, we present an account of the EPR spectra of P1 centers at ultra-high fields and show that the more complex spectra at 12-20 T are the result of significant state mixing in the mS = +1/2 electron spin manifold. The state mixing is a result of fulfilling the cancellation condition, meaning the e-14N hyperfine interaction equals twice the Larmor frequency of the 14N nuclear spin. We illustrate the influence of the cancellation condition on the EPR spectra by comparing EPR spectra acquired at 6.9 and 13.8 T. While the former are similar to the consensus spectra observed at lower fields, the latter are very different. We present numerical simulations that quantitatively account for the experimental spectra at both 6.9 and 13.8 T. Finally, we use electron electron double resonance (ELDOR) measurements to show that the cancellation condition results in increased spectral diffusion in the 13.8 T spectrum. This work sheds light on the spin properties of P1 centers under DNP-characteristic conditions, which will be conducive to their efficient utilization in DNP.

Improved Fourier Domain Model and Adaptive Controller Design for Handling Double Resonance Impact on Performance of Current-Fed Isolated DC/DC Converter

Improved Fourier Domain Model and Adaptive Controller Design for Handling Double Resonance Impact on Performance of Current-Fed Isolated DC/DC Converter

Spin labels for 19F ENDOR distance determination: resolution, sensitivity and distance predictability.

19F electron-nuclear double resonance (ENDOR) has emerged as an attractive method for determining distance distributions in biomolecules in the range of 0.7-2 nm, which is not easily accessible by pulsed electron dipolar spectroscopy. The 19F ENDOR approach relies on spin labeling, and in this work, we compare various labels' performance. Four protein variants of GB1 and ubiquitin bearing fluorinated residues were labeled at the same site with nitroxide and trityl radicals and a Gd(III) chelate. Additionally, a double-histidine variant of GB1 was labeled with a Cu(II) nitrilotriacetic acid chelate. ENDOR measurements were carried out at W-band (95 GHz) where 19F signals are well separated from 1H signals. Differences in sensitivity were observed, with Gd(III) chelates providing the highest signal-to-noise ratio. The new trityl label, OXMA, devoid of methyl groups, exhibited a sufficiently long phase memory time to provide an acceptable sensitivity. However, the longer tether of this label effectively reduces the maximum accessible distance between the 19F and the Cα of the spin-labeling site. The nitroxide and Cu(II) labels provide valuable additional geometric insights via orientation selection. Prediction of electron-nuclear distances based on the known structures of the proteins were the closest to the experimental values for Gd(III) labels, and distances obtained for Cu(II) labeled GB1 are in good agreement with previously published NMR results. Overall, our results offer valuable guidance for selecting optimal spin labels for 19F ENDOR distance measurement in proteins.

Homochiral vs. heterochiral preference in chiral self-recognition of cyclic diols.

The structure and clustering propensity of a chiral derivative of cis-1,2-cyclohexanediol, namely, 1-phenyl-cis-1,2-cyclohexanediol (cis-PCD), has been studied under supersonic expansion conditions by combining laser spectroscopy with quantum chemistry calculations. The presence of the phenyl substituent induces conformational locking relative to cis-1,2-cyclohexanediol (cis-CD), and only one conformer of the bare molecule is observed by both Raman and IR-UV double resonance spectroscopy. The homochiral preference inferred for the dimer formation at low enough temperature is in line with the formation of a conglomerate in the solid state. The change in clustering propensity in cis-PCD relative to trans-1,2-cyclohexanediol (trans-CD), which shows heterochiral preference, is explained by the presence of the phenyl substituent rather than the effect of cis-trans isomerism. Indeed the transiently chiral cis-CD also forms preferentially heterodimers, whose structure is very close to that of the corresponding trans-CD dimer.

Double resonance in seismo-lithosphere-atmosphere-ionosphere coupling

nvestigations into causal mechanisms behind anomalous pre-earthquake phenomena are considered a promising way of earthquake prediction. Numerous promising channels for seismo-lithosphere-atmosphere-ionosphere coupling have been proposed; however, predicting earthquakes remains a great challenge in the scientific society. Short-period ground vibrations exhibiting frequency characteristics similar to natural frequencies caused by strata failure resonance have recently been detected using tiltmeters embedded in magnetometers prior to earthquakes. These vibrations originate from regions near the epicentres of forthcoming earthquakes and can be simultaneously detected by broadband seismometers and ground-based global navigation satellite system (GNSS) receivers. Unlike the total electron contents (TECs) obtained from orbiting satellites, the vibrations and the identifiable TEC perturbations in data from geostationary satellites of the BeiDou Navigation System share frequencies prior to earthquakes. However, the causal relationship between the vibrations and TEC perturbations remains unclear due to a gap in data observations between the lithosphere and ionosphere. To address this issue, an instrumental array was established to monitor vibrations and perturbations in the lithosphere, atmosphere, and ionosphere. Observational data from the array partially fill the gap, and analytical results show that ground vibrations, air pressure, magnetic fields, and TEC data shared a common frequency of approximately 5 × 10–3 Hz (5 mHz) before major earthquakes. This suggests that the resonant ground vibrations trigger atmospheric resonance before earthquakes. Therefore, the double resonance (crustal and atmospheric resonance) model is a new explanation for the observed anomalies in multiple geophysical parameters in the lithosphere, atmosphere, and ionosphere. Retrieving resonant signals from multiple sources of observational data is a significant challenge, but once this issue is overcome, double resonance may contribute to practical earthquake prediction.

Tunable asymmetric square split ring resonator based triple band metamaterial absorber for wireless communication system

This article presents a triple band square split ring with double circular split ring resonator incident angle-insensitive perfect metamaterial absorber. The MMA unit cell was manufactured using a FR4 substrate that had dimensions of 8 mm by 8 mm. With the flexibility of on-design adjusting of the highest absorption frequencies, the suggested MA displays peak absorption of 99.67 %, 99.85 %, and 99.97 % at 2.52 GHz, 6.99 GHz, and 9.28 GHz, correspondingly. The tuning metallic two circular split rings and square split ring resonator provide the possibility of frequency modification throughout three distinct frequency ranges: the first frequency range extends from 2.45 GHz to 2.53 GHz, the second frequency range extends from 6.91 GHz to 7 GHz, and the third frequency range extends from 8.85 GHz to 10.32 GHz. Furthermore, the suggested MA displays near-zero absorption at an oblique incidence angle of up to 45° for both the TE as well as TM modes. The unit cell demonstrates single negative properties, such as an effective medium ratio (EMR) of 14.88 and a quality factor (Q factor) that is more than 30 for both the TM mode as well as the TE mode. An equivalent circuit successfully demonstrated its performance capability, which indicated that it would create an MMA of good quality when using ADS software. A comparison between the measured results of the suggested MMA and the simulated one reveals that there is a significant amount of a similarity between both of them. Because of its easy design within small dimension, wide angular stability, strong absorption, good EMR, and flexibility to frequency tuning is suitable for a wide range of wireless communication system, especially satellite applications like electromagnetic interference reduction, radar systems, imaging, and stealth technology.

3-Bit coded metasurface for linear and circular polarized vortex beam broadband modulation based on dual-frequency multistage resonance

A metasurface design scheme is proposed based on reflective double vertical U-shaped resonators. Compared to planar resonators with the same parameters, vertical meta-atom can excite magnetic dipole resonance and quaternary resonance respectively at low and high frequency to achieve stable wideband phase shift and unique free regulation. Vertical meta-atoms can be applied as 3-bit coding elements in linearly polarized (LP) and circularly polarized (CP) states with bandwidths of 0.7–1.1 THZ and 0.55–1.5 THZ, respectively. At the same time, as a half-wave plate, the deflection conversion rate is 95%, the relative bandwidth is 69%, and the operating Angle is 80°. In order to verify the application capability of the designed meta-atom, the excitation and separation of multi-stage vortex beams are performed in the wide frequency range of LP and CP using the coded convolutional addition method. The designed meta-atom only needs to regulate a single structural parameter to fully satisfy the requirements of 3-Bit broadband coding under LP and CP incidence, so it has multi-type polarization wave universality and ultra-wide working bandwidth. Meanwhile, the method can be effectively applied to optical band and microwave band.

High-efficiency electromagnetic energy harvesting using double-elliptical metasurface resonators.

This study introduces a metasurface (MS) based electrically small resonator for ambient electromagnetic (EM) energy harvesting. It is an array of novel resonators comprising double-elliptical cylinders. The harvester's input impedance is designed to match free space, allowing incident EM power to be efficiently absorbed and then maximally channelled to a single load through optimally positioned vias. Unlike the previous research works where each array resonator was connected to a single load, in this work, the received power by all array resonators is channelled to a single load maximizing the power efficiency. The performance of the MS unit cell, when treated as an infinite structure, is examined concerning its absorption and harvesting efficiency. The numerical results demonstrate that the MS unit cell can absorb EM power, with near-perfect absorption of 90% in the frequency range of 5.14 GHz to 5.5 GHz under normal incidence and with a fractional bandwidth of 21%. The MS unit cell also achieves higher harvesting efficiency at various incident angles up to 60o. The design and analysis of an array of 4x4 double elliptical cylinder MS resonators integrated with a corporate feed network are also presented. The corporate feed network connects all the array elements to a single load, maximizing harvesting efficiency. The simulation and measurement results reveal an overall radiation to AC efficiency of about 90%, making it a prime candidate for energy harvesting applications.

Broadband ventilated metamaterial absorber from non-local coupling

Due to its role in broadband impedance matching and acoustic modulations, the non-local couplings in acoustic metamaterials have received considerable attention recently. In previous research, there has been established a trade-off between absorption performance and geometric thickness. However, broadband absorption of sound energy under ventilation conditions with non-local couplings are yet explored. Here, we demonstrate unconventional double Helmholtz resonators with embedded apertures to achieve broadband absorption under a ventilated environment, whose absorption efficiency is robust to the change of ventilation ratio. Besides, different broadband working frequency ranges can be achieved by modulating the non-local coupling in different opening directions. Hence, our work provides a potential and promising method for attenuating broadband sound energy at low frequencies under various ventilation scenarios.

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

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.