Recombination Emission Research Articles

Donor–Acceptor Recombination Emission in Hydrogen‐Terminated Nanodiamond

AbstractFluorescence spectra of nanodiamonds synthesized at high pressure from adamantane and other organic compounds show narrow (≈1 nm) lines of unknown origin over the spectroscopic range from ≈500 to 800 nm. The study proposes and experimentally confirms the hypothesis that these lines are related to radiative recombination of donor–acceptor pairs (DAP). According to the experimental data, these pairs can be formed from donor‐like substitutional nitrogen present in the diamond lattice and 2D acceptor layer resulting from the effect of transfer doping on the nanodiamond surface. A peculiar behavior of the narrow lines is identified within the temperature range of 100–10 K: their energy position slightly shifts downward, and the majority of the lines divide into two or more components as the temperature decreases. The lines are shown to be predominantly associated with single photon emitters, with an emission rate exceeding 1 million counts s−1 at room temperature. A new narrowband source of room‐temperature fluorescence found in hydrogen‐terminated nanodiamonds push horizons for quantum optical technologies related to the development of single photon emitters and temperature nanosensors.

Measurement of Stark-split beam and carbon charge exchange emissions for simultaneous B-field and temperature/rotation analysis at DIII-D.

A set of two newly designed, single-channel Czerny-Turner spectrometers has been deployed at the DIII-D tokamak for measurements of the motional Stark effect (MSE) split beam emission and the C6+ (CVI) carbon charge exchange recombination (CER) emission at high spectral (δλ = 0.13nm) and temporal (1-5kHz) resolution. High throughput optics (f/# = 2.8) allow for good signal-to-noise at high time resolution using fast EMCCD detectors. The MSE emission allows for spectral fitting of the magnitude and direction of the local B-field, while the carbon emission yields local ion temperature and toroidal rotation information. To reduce so-called Doppler broadening of the MSE emission, a new channel-specific variable lens-masking approach has been developed. Experimental data collected from the 2023 DIII-D experimental campaign demonstrate the signal quality and instrument fidelity for both diagnostic measurements. Moreover, initial CER data analysis shows a clear evolution of the toroidal rotation during edge localized modes. Initial progress on the advanced MSE model, including a new validated ray-trace model of the DIII-D collection optics, is shown via sensitivity analysis.

Ligand Controls Excited Charge Carrier Dynamics in Metal-Rich CdSe Quantum Dots: Computational Insights.

Small metal-rich semiconducting quantum dots (QDs) are promising for solid-state lighting and single-photon emission due to their highly tunable yet narrow emission line widths. Nonetheless, the anionic ligands commonly employed to passivate these QDs exert a substantial influence on the optoelectronic characteristics, primarily owing to strong electron-phonon interactions. In this work, we combine time-domain density functional theory and nonadiabatic molecular dynamics to investigate the excited charge carrier dynamics of Cd28Se17X22 QDs (X = HCOO-, OH-, Cl-, and SH-) at ambient conditions. These chemically distinct but regularly used molecular groups influence the dynamic surface-ligand interfacial interactions in Cd-rich QDs, drastically modifying their vibrational characteristics. The strong electron-phonon coupling leads to substantial transient variations at the band edge states. The strength of these interactions closely depends on the physicochemical characteristics of passivating ligands. Consequently, the ligands largely control the nonradiative recombination rates and emission characteristics in these QDs. Our simulations indicate that Cd28Se17(OH)22 has the fastest nonradiative recombination rate due to the strongest electron-phonon interactions. Conversely, QDs passivated with thiolate or chloride exhibit considerably longer carrier lifetimes and suppressed nonradiative processes. The ligand-controlled electron-phonon interactions further give rise to the broadest and narrowest intrinsic optical line widths for OH and Cl-passivated single QDs, respectively. Obtained computational insights lay the groundwork for designing appropriate passivating ligands on metal-rich QDs, making them suitable for a wide range of applications, from blue LEDs to quantum emitters.

Toward Exoplanet Transit Spectroscopy Using JWST/MIRI’s Medium Resolution Spectrometer

The Mid-Infrared Instrument Medium Resolution Spectrometer (the MRS) on JWST has potentially important advantages for transit and eclipse spectroscopy of exoplanets, including lack of saturation for bright host stars, wavelength span to longward of 20 µm, and JWST’s highest spectral resolving power. We here test the performance of the MRS for time series spectroscopy by observing the secondary eclipse of the bright stellar eclipsing binary R Canis Majoris. Our observations push the MRS into saturation at the shortest wavelength, more than for any currently known exoplanet system. We find strong charge migration between pixels that we mitigate using a custom data analysis pipeline. Our data analysis recovers much of the spatial charge migration by combining detector pixels at the group level, via weighting by the point-spread function. We achieve nearly photon-limited performance in time series data at wavelengths longward of 5.2 µm. In 2017, Snellen et al. suggested that the MRS could be used to detect carbon dioxide absorption from the atmosphere of the temperate planet orbiting Proxima Centauri. We infer that the relative spectral response of the MRS versus wavelength is sufficiently stable to make that detection feasible. As regards the secondary eclipse of this Algol-type binary, we measure the eclipse depth by summing our spectra over the wavelengths in four channels, and also measuring the eclipse depth as observed by TESS. Those eclipse depths require a temperature for the secondary star that is significantly hotter than previous observations in the optical to near-IR, probably due to irradiation by the primary star. At full spectral resolution of the MRS, we find atomic hydrogen recombination emission lines in the secondary star, from principal quantum levels n = 7, 8, 10, and 14.

JWST-FEAST: Feedback in Emerging extrAgalactic Star clusTers: Calibration of Star Formation Rates in the Mid-infrared with NGC 628

New JWST near-infrared imaging of the nearby galaxy NGC 628 from the JWST Cycle 1 program Feedback in Emerging extrAgalactic Star clusTers (JWST-FEAST) is combined with archival JWST mid-infrared imaging to calibrate the 21 μm emission as a star formation rate (SFR) indicator at ∼120 pc scales. The Paα (1.8756 μm) hydrogen recombination emission line targeted by FEAST provides a reference SFR indicator that is relatively insensitive to dust attenuation, as demonstrated by combining this tracer with Hubble Space Telescope Hα imaging. Our analysis is restricted to regions that appear compact in nebular line emission and are sufficiently bright to mitigate effects of both age and stochastic sampling of the stellar initial mass function. We find that the 21 μm emission closely correlates with the nebular line emission, with a power law with exponent = 1.07 ± 0.01, in agreement with past results. We calibrate a hybrid SFR indicator using a combination of Hα and 24 μm (extrapolated from 21 μm) tracers and derive the proportionality constant between the two tracers, b = 0.095 ± 0.007, which is ∼3–5 times larger than previous derivations using large regions/entire galaxies. We model these discrepancies as an increasing contribution to the dust heating by progressively older stellar populations for increasing spatial scale, in agreement with earlier findings that star formation is hierarchically distributed in galaxies. Thus, the use of hybrid SFR indicators requires prior knowledge of the mean age of the stellar populations dominating the dust heating, which makes their application uncertain. Conversely, nonlinear calibrations of SFRs from L(24) alone are more robust, with a factor ≲ 2.5 variation across the entire range of L(24) luminosities from H ii regions to galaxies.

Evaluation of the effect of oxygen addition on charge carrier transport properties in single-crystal diamond growth

The effects of oxygen addition during single-crystal diamond growth by microwave plasma CVD method on crystal surface morphology and charge carrier transport properties were evaluated. Diamond single-crystals were homoepitaxially grown on (001) surface of high-pressure and high-temperature (HPHT) synthesized type IIa single-crystal diamond substrates with a fixed methane concentration of 1 % and oxygen concentrations of 0–0.8 %. Inverted pyramid-shaped pits were generated as the oxygen concentration increased. The free exciton recombination emission intensity in the cathodoluminescence spectrum reached a maximum at oxygen concentration of 0.5 %. The samples with oxygen concentrations of 0.5 % and 0.8 % showed excellent charge collection efficiency and energy resolution. On the other hand, the mobility-lifetime (μτ) product was only (7.1 ± 1.7) × 10−5 cm2/V, which is approximately 1/4 of that of the sample with 0.2 % methane and no oxygen addition.

All‐Inorganic Cs2YbCl5·H2O Perovskite with Luminescence Response to Methanol for Anti‐Counterfeiting

AbstractStimuli‐responsive luminescent materials have attracted much research attention due to their wide application potential in various fields. Typically, the family of hydrated double perovskite A2MIIIX5·H2O shows unique emission color transformation between hydrated and dehydrated complexes, highlighting the application potential in advanced anti‐counterfeiting. Herein, two zero‐dimensional perovskites of Cs2YbCl5·H2O and Cs3YbCl6, are reported and broad‐band self‐trapped exciton recombination emission can be realized via external Sb3+ doping. Intriguingly, the Cs2YbCl5·H2O can be transformed to the dehydrated counterpart of Cs3YbCl6 through a facile methanol treatment at room temperature, leading to the emission color transformation from yellow to green. Notably, the green‐emissive Cs3YbCl6:Sb3+ delivers a high photoluminescence quantum yield of 67.3%. Leveraging the advantages of obvious methanol‐induced emission color transformation between Cs2YbCl5·H2O and Cs3YbCl6 at room temperature, Cs2YbCl5·H2O can be used in the field of high‐security‐level anti‐counterfeiting.

Ambipolar Charge Injection and Bright Light Emission in Hybrid Oxide/Polymer Transistors Doped with Poly(9‐Vinylcarbazole) Based Polyelectrolytes

AbstractLight‐emitting transistors (LETs) are a remarkable, emerging class of electronic devices that combine the switching function of field‐effect transistors (FETs) and the light‐emitting function of light‐emitting diodes (LEDs). In order to achieve efficient light emission, effective electron and hole injection from source and drain electrodes is necessary. Various strategies have been introduced to accomplish this, such as incorporating asymmetric electrodes or charge injection layers during device fabrication. These approaches have inevitably introduced complexity in the device fabrication process. Herein, light‐emitting electrochemical transistors (LECTs) are demonstrated that combine principles of electrochemistry and optoelectronics to achieve multi‐functionality in a simple device architecture. Hybrid polyelectrolytes, poly(9‐vinylcarbazolesulfonate)‐ lithium and copper (II) salts (PVK‐Li and PVK‐Cu) incorporating Li+ ion and Cu2+ ions are added at variable concentrations to the organic emitting layer of LECTs to effect electrochemical p‐type doping. This electrochemical doping approach yielded improvements in electrical and optical performances including mobilities, brightnesses, and external quantum efficiency of the LECTs. The dynamics of how charges including ions, electrons, and holes move and interact are discussed in the device to facilitate emissive charge carrier recombination and light emission. This investigation provides valuable insights into the realms of both electrochemistry and optoelectronics.

JADES: The emergence and evolution of Lyα emission and constraints on the intergalactic medium neutral fraction

The rest-frame UV recombination emission line Lyα can be powered by ionising photons from young massive stars in star-forming galaxies, but the fact that it can be resonantly scattered by neutral gas complicates its interpretation. For reionisation-era galaxies, a neutral intergalactic medium will scatter Lyα from the line of sight, making Lyα a useful probe of the neutral fraction evolution. Here, we explore Lyα in JWST/NIRSpec spectra from the ongoing JADES programme, which targets hundreds of galaxies in the well-studied GOODS-S and GOODS-N fields. These sources are UV-faint (−20.4 < MUV < −16.4) and thus represent a poorly explored class of galaxy. We fitted the low spectral resolution spectra (R ∼ 100) of a subset of 84 galaxies in GOODS-S with zspec > 5.6 (as derived with optical lines) with line and continuum models to search for significant line emission. Through exploration of the R100 data, we find evidence for Lyα in 17 sources. This sample allowed us to place observational constraints on the fraction of galaxies with Lyα emission in the redshift range 5.6 < z < 7.5, with a decrease from z = 6 to z = 7. We also find a positive correlation between the Lyα equivalent width and MUV, as seen in other samples. We used these results to estimate the neutral gas fraction at z ∼ 7, and our estimates are in agreement with previous results (XHI ∼ 0.5 − 0.9).

Origin and Composition of the Galactic Diffuse X-Ray Emission Spectra by Unresolved X-Ray Sources

Galactic diffuse X-ray emission (GDXE) can be spatially segmented into Galactic center X-ray emission (GCXE), Galactic ridge X-ray emission (GRXE), and Galactic bulge X-ray emission (GBXE). The X-ray spectra of GDXE are expressed by the assembly of compact X-ray sources, which are either white dwarfs (WDs) or X-ray active stars consisting of binaries with late-type stars. WDs have either a strong magnetic field or a weak magnetic field. WDs and X-ray active stars are collectively called compact X-ray stars. However, spectral fittings by the assembly of all compact X-ray stars for GCXE, GRXE, and GBXE are rejected, leaving significant excess near the energies of the Kα, Heα, and Lyα lines. These excesses are found in the collisional ionization equilibrium (CIE) plasma. Thus, the spectra of GRXE and GBXE are improved by adding CIE supernova remnants (SNRs). However, the GCXE spectrum is still unacceptable, with significant data excess due to radiative recombination emission (recombining plasma (RP)). The GCXE fit is then significantly improved by adding aged RP-SNRs. Aged RP-SNRs are made by a past big flare of Sgr A* emitting either hard X-rays or low-energy cosmic rays. The big flares may excite Fe and Ni atoms in cold diffuse gas (cold matter (CM)) and emit fluorescent X-ray lines. The CIE-SNRs, RP-SNRs, and CM are called diffuse X-ray sources. This paper presents the spectral fits by the assembly of all the compact and diffuse X-ray sources together with high-quality spectra and a combined fit among all the GDXE of GCXE, GRXE, and GBXE. This provides the first scenario to quantitatively and comprehensively predict the origin of the GDXE spectra.

New emission band of solid nitrogen

New results on the study of radiation effects in solid nitrogen and N2-doped Ne matrix are presented, with a focus on the so-called γ-line origin. The irradiation was carried out in dc regime with an electron beam of subthreshold energy. The relaxation dynamics was monitored by emission spectroscopy: cathodoluminescence (CL) and nonstationary luminescence (NsL), along with current activation spectroscopy. Thermally stimulated luminescence (TSL) and exoelectron emission (TSEE) of pure nitrogen and N2 in the Ne matrix were measured in a correlated manner. Three emission bands were recorded in the NIR CL spectra of solid N2: 794, 802, and 810 nm. The band at 810 nm was detected for the first time. These three bands are characterized by similar behavior and form molecular series with spacing between adjacent vibrational energy levels of the ground state of 125 and 123 cm−1. These data cast doubt on the recently made assumption that the γ-line is attributed to the emission of the nitrogen anion N− [R. E. Boltnev, I. B. Bykhalo, I. N. Krushinskaya et al. Phys. Chem. Chem. Phys. 18, 16013 (2016)]. The processes of electron attachment and neutralization of positively charged species are discussed. It has been established that the γ-line in the TSL spectra of pure nitrogen and N2-doped Ne matrix correlates with TSEE currents and recombination emission of O+, N2+, and N4+ ions, which indicates its connection with the neutralization reaction. The measurement of NsL supported this conclusion. A new possible assignment of the γ-line and its satellites to the emission of tetranitrogen N4 is discussed.

Subnanosecond switching of GaAs diode due to impact ionization in collapsing bipolar Gunn domains

Subnanosecond switching of high-voltage GaAs diodes initiated by a steep reverse voltage ramp (≥1 kV/ns) is investigated experimentally and numerically. The triggering occurs at the voltage Um which exceeds stationary breakdown voltage Ub, similar to delayed impact ionization breakdown in Si picosecond-range high-voltage diodes known as silicon avalanche sharpening (SAS) diodes. Despite this similarity, we argue that the triggering mechanism of GaAs diodes is qualitatively different and is based on negative differential electron mobility in GaAs. Spatial patterns of recombination emission indicate formation of narrow conducting channels. Numerical simulations reveal the spontaneous appearance of high-field (∼400 kV/cm) bipolar Gunn domains in these channels. The agreement of experiments and simulations demonstrates that impact ionization within collapsing Gunn domains is responsible for a rapid increase of nonequilibrium carrier concentration and subnanosecond switching of the reversely biased GaAs diode to the conducting state with low (<100 V) residual voltage. In particular, the proposed mechanism explains why GaAs diodes exhibit subnanosecond switching at moderate overvoltage ratio Um/Ub ≈ 1.5 smaller than typical overvoltage Um/Ub ≈ 2 required for switching Si diodes, and the origin of anomalous delay of several nanoseconds that is experimentally observed in such regimes.

Effect of Plasma Treatment on the Luminescent and Scintillation Properties of Thick ZnO Films Fabricated by Sputtering of a Hot Ceramic Target

The paper presents the results of a comprehensive study of the structural-phase composition, morphology, optical, luminescent, and scintillation characteristics of thick ZnO films fabricated by magnetron sputtering. By using a hot ceramic target, extremely rapid growth (~50 µm/h) of ZnO microfilms more than 100 µm thick was performed, which is an advantage for the industrial production of scintillation detectors. The effects of post-growth treatment of the fabricated films in low-temperature plasma were studied and a significant improvement in their crystalline and optical quality was shown. As a result, the films exhibit intense near-band-edge luminescence in the near-UV region with a decay time of &lt;1 ns. Plasma treatment also allowed to significantly weaken the visible defect luminescence excited in the near-surface regions of the films. A study of the luminescence mechanisms in the synthesized films revealed that their near-band-edge emission at room temperature is formed by phonon replicas of free exciton recombination emission. Particularly, the first phonon replica plays the main role in the case of optical excitation, while upon X-ray excitation, the second phonon replica dominates. It was also shown that the green band peaking at ~510 nm (2.43 eV) is due to surface emission centers, while longer wavelength (&gt;550 nm) green-yellow emission originates mainly from bulk parts of the films.

Modelling variable linear polarization produced by Co-rotating Interaction Regions (CIRs) across optical recombination lines of Wolf–Rayet stars

ABSTRACT Massive star winds are structured both stochastically (‘clumps’) and often coherently (Co-rotation Interaction Regions, or CIRs). Evidence for CIRs threading the winds of Wolf–Rayet (WR) stars arises from multiple diagnostics including linear polarimetry. Some observations indicate changes in polarization position angle across optical recombination emission lines from a WR star wind but limited to blueshifted Doppler velocities. We explore a model involving a spherical wind with a single conical CIR stemming from a rotating star as qualitative proof-of-concept. To obtain a realistic distribution of limb polarization and limb darkening across the pseudo-photosphere formed in the optically thick wind of a WR star, we used Monte Carlo radiative transfer (MCRT). Results are shown for a parameter study. For line properties similar to WR 6 (EZ CMa; HD 50896), combining the MCRT results, a simple model for the CIR, and the Sobolev approximation for the line formation, we were able to reproduce variations in both polarization amplitude and position angle commensurate with observations. Characterizing CIRs in WR winds has added importance for providing stellar rotation periods since the vsin i values are unobtainable because the pseudo-photosphere forms in the wind itself.

Intrinsic emissions and formation of electron-hole trapping centres in excited Li2SO4

Vacuum ultraviolet and thermal activation spectroscopies were used to study the nature of intrinsic emission and the mechanisms of the formation of electron and hole trapping centres in irradiated Li2SO4 powders and crystals. The obtained results along with excitation spectra showed that recombination emission at 3.8–4.2 eV and 4.5–5.5 eV occurs when an electron passes from the second and third sub-bands of the valence band formed from the 2p state of oxygen to the conduction band. It has been determined that Li2SO4 electron and hole trapping centres are created when electrons are trapped in the SO42– anionic sites. The holes are localised in the form of SO4 – radicals. The spectral position and intensity of individual emission bands are dependent on the crystallographic arrangement of localised holes.

Temperature-dependent electroluminescence of a gate pulsed silicon carbide metal–oxide–semiconductor field-effect transistor: Insight into interface traps

Switching a silicon carbide (SiC) metal–oxide–semiconductor field-effect transistor between inversion and accumulation with removed drain and grounded source terminals leads to defect-assisted carrier recombination and light emission. The energy spectrum of the emitted photons provides valuable information on the involved defects, located both at the 4H-SiC/SiO2 interface and in the 4H-SiC bulk. Here, we measured and analyzed the emitted light over a broad temperature range between 12 and 297 K. Our results reveal two local maxima in light intensity around 30 and 140 K. Most importantly, the local intensity maxima and the related temperatures correlate with both the overall recombination current and gate capacitance measurements. The spectral analysis allowed us to distinguish between recombinations occurring on 4H-SiC bulk defects and 4H-SiC/SiO2 interface-related defects. We explain an initial increase of light emission with decreasing temperature to competing non-radiative pathways with activation energies of 34 and 60 meV for SiC/SiO2 interface- and 4H-SiC bulk-related emissions, respectively. Based on an extensive literature review, we link the measured photon emission to donor–acceptor pair recombination, the EH6/7 or the Z1/2 defect centers. In addition to that, we could link a prominent peak at 2.915 eV to the L1 line of the D1-center. Most importantly, we conducted our own ab initio simulations revealing that recombination via PbC-centers, previously identified with carbon dangling bonds at the 4H-SiC/SiO2 interface [Cottom et al., J. Appl. Phys. 124, 045302 (2018)], could also provide an explanation for the photon emission around 1.75 eV. Finally, our simulation of an interface-related silicon vacancy VSi,I reveals a radiative transition around 2.8 eV.

Coal humus acid functionalized high stability fluorescent copper nanoclusters for tumor identification by sequential off-on-off monitoring tryptophan and Hg2.

The abnormalities of Tryptophan (Trp) and mercury ions (Hg2+) not only easily activate diseases, including mental illness and cancer, but also seriously affect human wellbeing. Fluorescent sensors are profoundly attractive options for identifying amino acids and ions; however, most sensors remain challenging due to the multipliable cost and deviation from the asynchronous quenching detection. In particular, fluorescent copper nanoclusters with high stability that quantitatively monitoring Trp and Hg2+ successively have seldom been reported. Herein, we employ coal humus acid (CHA) as a protective ligand and successfully construct weak cyan fluorescent copper nanoclusters (CHA-CuNCs) by a rapid, environmentally benign and cost-effective method. Significantly, the fluorescence of CHA-CuNCs is obviously improved by introducing Trp, because the indole group of Trp enhances the radiative recombination and aggregation-induced emissions. Interestingly, CHA-CuNCs not only realizes the highly selective and specific detection of Trp with a linear range of 25-200μM and a detection limit of 0.043μM based on the turn-on fluorescence strategy, but also quickly achieves the consecutive turn-off detection of Hg2+ due to the chelation interaction between Hg2+ and pyrrole heterocycle in Trp. Moreover, this method is successfully applied in the analysis of Trp and Hg2+ in real samples. Furthermore, the confocal fluorescent imaging of tumor cells demonstrates that CHA-CuNCs can be used for bioimaging and cancer cell recognition with Trp and Hg2+ abnormalities. These findings provide new guidance for the eco-friendly synthesis of CuNCs with eminent sequential off-on-off optical sensing property, indicating good prospects in biosensing and clinical medicine applications.

Electron-hole trapping centers in Na2SO4 with a transition metal impurity Mn

The Na 2 SO 4 samples were obtained by slow evaporation method. The mechanisms of the formation of electron and hole trapping centers are investigated by spectroscopic methods. Intrinsic recombination emission of 2.9–3.1 eV and impurity emission of 1.85 eV are excited at 4.0–4.5 eV. Intrinsic SO 3− 4 −SO − 4 and impurity Mn + − SO − 4 trapping centers were revealed. The local levels corresponding between the electron and hole trapping center are 4.0–4.5 eV. The decay of intrinsic and impurity trapping centers was recorded at temperatures of 130–150 K and 280–350 K.

Recombination Emission of Quantum Wires in Electric Field and Prospects for Its Lasing

Recombination Emission of Quantum Wires in Electric Field and Prospects for Its Lasing

GOALS-JWST: Tracing AGN Feedback on the Star-forming Interstellar Medium in NGC 7469

We present James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI) integral-field spectroscopy of the nearby merging, luminous infrared galaxy, NGC 7469. This galaxy hosts a Seyfert type-1.5 nucleus, a highly ionized outflow, and a bright, circumnuclear star-forming ring, making it an ideal target to study active galactic nucleus (AGN) feedback in the local universe. We take advantage of the high spatial/spectral resolution of JWST/MIRI to isolate the star-forming regions surrounding the central active nucleus and study the properties of the dust and warm molecular gas on ∼100 pc scales. The starburst ring exhibits prominent polycyclic aromatic hydrocarbon (PAH) emission, with grain sizes and ionization states varying by only ∼30%, and a total star formation rate of 10–30 M ⊙ yr−1 derived from fine structure and recombination emission lines. Using pure rotational lines of H2 we detect 1.2 × 107 M ⊙ of warm molecular gas at a temperature higher than 200 K in the ring. All PAH bands get significantly weaker toward the central source, where larger and possibly more ionized grains dominate the emission, likely the result of the ionizing radiation and/or the fast wind emerging from the AGN. The small grains and warm molecular gas in the bright regions of the ring however display properties consistent with normal star-forming regions. These observations highlight the power of JWST to probe the inner regions of dusty, rapidly evolving galaxies for signatures of feedback and inform models that seek to explain the coevolution of supermassive black holes and their hosts.