Fluorescence Photons Research Articles

Enhancing nondestructive mass identification via Fourier-transform fluorescence analysis

Single-ion mass identification is important for atomic and nuclear physics experiments on ions produced with low yields. Cooling the ion to ultralow temperatures through interaction with a laser-cooled ion will enhance the precision of the measurements. In this paper we present axial-common-mode frequency measurements of balanced and unbalanced Coulomb crystals from the Fourier transform of the fluorescence photons from a Doppler-cooling transition in calcium ions after probing the ion crystal with a five-radio-frequency comb. A single ion nondestructively detected can be used for identification, yielding a mass-resolving power m/ΔmFWHM≈310 from the axial common mode. This identification can be performed from a single measurement within times below 1 s. Published by the American Physical Society 2024

Simultaneous 2-photon and 3-photon excitation with a red fluorescent protein-cyanine dye probe pair in the 1700-nm excitation window for deep in vivo neurovascular imaging

In vivo imaging of the neurovascular network is considered to be one of the most powerful approaches for understanding brain functionality. Nevertheless, simultaneously imaging the biological neural network and blood vessels in deep brain layers in a non-invasive manner remains to a major challenge due to the lack of appropriate labeling fluorescence probe pairs. Herein, we proposed a 2-photon and 3-photon fluorescence probe pair for neurovascular imaging. Specifically, the red fluorescence protein (RFP) with an absorption maximum of around 550 nm is used as a 3-photon excited probe to label neurons, and a cyanine derivative dye Q820@BSA has a NIR absorption maximum of 825 nm as a 2-photon excited probe to label the vasculature, enabling single wavelength excitation at 1650 nm for neurovascular imaging with high emission spectral separation (>250 nm). In particular, the 2-photon action cross-section of Q820@BSA was found to be about 2-fold larger than that of indocyanine green (ICG), a commonly used red 2-photon fluorescence labeling agent, at the same excitation wavelength. Benefiting from the long wavelength advantage in reducing scattering in both 2 and 3-photon excitation of the fluorescence pairs, we demonstrated in vivo neurovascular imaging in intact adult mouse brains through white matter and deep into the hippocampus in the somatosensory cortex.

Label-Free Optical Biopsy Reveals Biomolecular and Morphological Features of Diabetic Kidney Tissue in 2D and 3D.

Kidney disease, the ninth leading cause of death in the United States, has one of the poorest diagnostic efficiencies of only 10%1. Conventional diagnostic methods often rely on light microscopy analysis of 2D fixed tissue sections with limited molecular insight compared to omics studies. Targeting multiple features in a biopsy using molecular or chemical reagents can enhance molecular phenotyping but are limited by overlap of their spatial and chromatic properties, variations in quality of the products, limited multimodal nature and need additional tissue processing. To overcome these limitations and increase the breadth of molecular information available from tissue without an impact on routine diagnostic workup, we implemented label-free imaging modalities including stimulated Raman scattering (SRS) microscopy, second harmonic generation (SHG), and two photon fluorescence (TPF) into a single microscopy setup. We visualized and identified morphological, structural, lipidomic, and metabolic biomarkers of control and diabetic human kidney biopsy samples in 2D and 3D at a subcellular resolution. The label-free biomarkers, including collagen fiber morphology, mesangial-glomerular fractional volume, lipid saturation, redox status, and relative lipid and protein concentrations in the form of Stimulated Raman Histology (SRH), illustrate distinct features in kidney disease tissues not previously appreciated. The same tissue section can be used for routine diagnostic work up thus enhancing the power of cliniopathological insights obtainable without compromising already limited tissue. The additional multimodal biomarkers and metrics are broadly applicable and deepen our understanding of the progression of kidney diseases by integrating lipidomic, fibrotic, and metabolic data.

Multi‐Channel Optical Encryption Film With Strong Circularly Polarized Luminescence and High Quantum Yield

AbstractDeveloping a sustainable security module with multiple optical states is important to deter counterfeits, but is challenging. This work designs a kind of chiral luminescent film through the co‐assembly of the CNCs and d‐glucose, simultaneously doped with the lanthanide complex and organic dye. Superior mechanical performance makes it undertake various deformations, including twist, and tension without breaking. Meanwhile, this film has unique optical characteristics. On the one hand, the chiroptical signals can be manipulated through the matching of the photonic bandgap and fluorescence peak. On the other hand, due to the co‐assembly with two luminophores, the film displays the excitation wavelength (Ex)‐dependent circularly polarized luminescence properties. Under the Ex of 275 nm, the film simultaneously integrates a large dissymmetry factor of −0.3898, a high quantum yield of 69.19%, and a considerable lifetime of 1381 µs, which has exceeded most reported chiral luminescent assemblies. These multimodal and convertible optics endow the film with practical applications in the anti‐counterfeit. It can be designed as a security label or used as a written paper to encrypt the information. Even in humid surroundings, this security effect is still ensured.

Observation of Three-Photon Cascaded Emission from Triexcitons in Giant CsPbBr3 Quantum Dots at Room Temperature.

Colloidal semiconductor nanocrystals have long been considered a promising source of time-correlated and entangled photons via the cascaded emission of multiexcitonic states. The spectroscopy of such cascaded emission, however, is hindered by efficient nonradiative Auger-Meitner decay, rendering multiexcitonic states nonemissive. Here we present room-temperature heralded spectroscopy of three-photon cascades from triexcitons in giant CsPbBr3 nanocrystals. We show that this system exhibits second- and third-order correlation function values, g(2)(0) and g(3)(0,0), close to unity, identifying very weak binding of both biexcitons and triexcitons. Combining fluorescence lifetime analysis, photon statistics, and spectroscopy, we can readily identify emission from higher multiexcitonic states. We use this to verify emission from a single emitter despite high emission quantum yields of multiply excited states and comparable emission lifetimes of singly and multiply excited states. Finally, we present potential pathways toward control of the photon number statistics of multiexcitonic emission cascades.

Investigation of Energy Deposition by Soft X-rays into Solar Cell Materials

A high-altitude nuclear detonation releases a significant portion of energy as X-rays with a blackbody spectrum. Satellites are particularly vulnerable to prompt soft X-rays (~1 keV) absorbed within a few microns of the surface of the solar array, causing melting and evaporation of its materials. The absorption of soft X-rays in solar cell materials is studied using GEANT4 computer software. Energy deposition as a function of depth (depth-dose profile) is calculated for slab geometries of dielectric and metallic materials. The photo-absorption and Compton scattering of X-rays and the contribution of secondary radiation, such as photo-electrons, Auger-electrons, and fluorescence photons are taken into account. The effect of the production of secondary radiation on the distribution of deposited dose in the near-surface region of materials is investigated. The results presented in this work are validated against published data and provide valuable insights into X-ray absorption by solar cell materials, the redistribution of energy by secondary radiation, and the spatial scale of power density deposition that can be used as a source term for the further thermomechanical analysis of a material’s phase transformations and melting.

Use of the 5P3/2→6P3/2 electric dipole forbidden transition in Rb as a non-perturbing probe of atom dynamics in an operating magneto-optical trap

Abstract Results of spectroscopy experiments using the $5P_{3/2} \to 6P_{3/2}$ electric dipole forbidden transition in cold rubidium atoms are presented. Production of this forbidden transition is detected by observing the emission of the $420 $ nm fluorescence photons that result from the decay of the $6P_{3/2} $ state into the ground state. The experiments are performed under the steady state operation conditions of a magneto-optical trap (MOT), and thus provide non-perturbing information on the atom-light system. The hyperfine structure of the $6P_{3/2}$ level is completely resolved, and the fluorescence peaks show the expected Autler-Townes (AT) splitting of the emission lines. This hyperfine structure is used to calibrate the frequency scale of all spectra recorded. A combination of this absolute frequency scale and an expression for the AT profile allows an absolute determination of the effective Rabi frequency and detuning of the MOT. The behavior of these AT doublets is studied as a function of frequency detuning and also as a function of the trapping light intensity.
The experiments also take full advantage of the strong polarization dependence of the relative intensities of the hyperfine fluorescence components.
This study results in a sensitive probe of the relative populations of the magnetic sublevel projections relative to the trapping magnetic field gradient.
An almost isotropic population distribution was found, but small deviations from isotropy could be determined with this electric dipole forbidden probe.

Quantum jump photodetector for narrowband photon counting with a single atom

Using a single neutral Rb87 atom held in an optical trap, and “quantum jump” detection of single-photon-initiated state changes, we demonstrate a single-photon quantum jump photodetector (QJPD) with intrinsically narrow bandwidth and strong rejection of out-of-band photons, of interest for detecting weak optical signals in the presence of a strong broadband background. By analyzing fluorescence photon count distributions for the bright and dark states with and without excitation, we measure quantum efficiency of 2.9(2)×10−3, a record for single-pass quantum jump production, and signal-photon-unprovoked “dark jump” rate—analogous to the dark count rate of other detectors —of 3(10)×10−3jumps/s during passive accumulation plus 4.0(4)×10−3 jumps per readout, orders of magnitude below those of traditional single-photon detectors. Available methods can substantially improve QJPD quantum efficiency, dark jump rate, bandwidth, and tunability. Published by the American Physical Society 2024

Development of a Monte Carlo simulation platform for the systematic evaluation of photon-counting detector-based micro-CT

PurposeThis study aimed to develop a photon-counting detector (PCD) based micro-CT simulation platform for assessing the performance of three different PCD sensor materials: cadmium telluride (CdTe), gallium arsenide (GaAs), and silicon (Si). The evaluation encompasses the components of primary and scatter signals, performance of imaging contrast agents, and detector efficiency. MethodsSimulations were performed using the Geant4 Monte Carlo toolkit, and a micro-PCD-CT system was meticulously modeled based on realistic geometric parameters. Results.The simulation can obtain HU values consistent with measured results for iodine and calcium hydroxyapatite contrast agents. The two major components of scatter signals for CdTe and GaAs based PCD are fluorescent X-ray photons and photoelectrons, whereas for Si, the components are photoelectrons and Compton electrons. Scattering counts of CdTe and GaAs sensors can be effectively reduced by using energy thresholds, whereas those of Si sensor are insensitive to the applied threshold. The optimal threshold values for CdTe and GaAs are 30 and 15 keV, respectively. For contrast agent imaging, GaAs exhibits enhanced sensitivity to low photon energies compared to CdTe, while it’s contrast-to-noise ratio (CNR) values are slightly lower than those of CdTe at the same contrast agent concentration. Among the three sensor materials, Si has the lowest CNR and detector efficiency; CdTe exhibits the highest efficiency, except in low-energy ranges (< 45 keV), where GaAs has superior efficiency. ConclusionsThe proposed methods are expected to benefit PCD optimization and applications, including energy threshold selection, scattering correction, and may reduce the need for large-scale experiments.

Informing solar blind radioluminescence imaging through a calibrated spectrum

While direct radiation detection methods offer great insight into the origin of ionizing particles and photons, their use to locate contaminated areas or concealed radioactive sources can lead to undue exposure of personnel and equipment to ionizing radiation or the potential for contamination. These same sources induce ultraviolet (UV) optical photon fluorescence in air – a process referred to as radioluminescence – that may be imaged from low dose regions over larger attenuation lengths than ionizing radiation. However, most optical detection methods are limited to low lighting conditions to image the more abundant ultraviolet-A (UV-A) photons. To extend this capability to room light or daytime conditions, the solar blind region (Ultraviolet-C (UV–C), <280 nm) can be tapped. Though the emission yield of UV-C photons is roughly two orders of magnitude lower than that in the UV-A regime, the UV-C offers dramatic improvements in signal-to-noise ratios under bright lighting conditions due to decreased background interferences. The yield of specific UV-C lines, if present in the literature at all, varies widely, which has a large impact in modeling and analyzing standoff UV-C measurement scenarios. Thus, we have captured improved radioluminescence spectra over 250–400 nm and identified observed emission peaks in ambient air. Many of the UV-C photons produced by ionizing radiation excitation result from high-energy, molecular nitrogen Gaydon-Herman transitions which have had limited study to date for this application. Relating these findings to published UV-A yields, we estimate emissions between 0.15 and 0.19 photons/MeV over 250–280 nm. We also use a commercial corona-discharge imaging camera to demonstrate outdoor UV-C radiation mapping of alpha and gamma emitters from 50 to 75 m standoffs, respectively. The imaged “counts” are compared to optically modeled values and show the same trend over distance.

Morphological insights into uncompetitive fluorescence of coal-based carbon dots and strategies for improvement

The findings of the research indicate that coal-derived carbon dots (CDs), produced through top-down methods, exist as a blend of graphene quantum dots (GQDs), carbon quantum dots (CQDs), and carbon nanodots (CNDs). Within this mixture, numerous individual particles are dispersed, each containing multiple sp2-carbon domains, suggesting the presence of multiple fluorescent centers of varying sizes. These fluorescent centers scatter photon energy, leading to a wide full width at half maximum (FWHM >80 nm). To tackle this issue, the study significantly improves the fluorescence efficiency of coal-based CDs by employing a nitrogen-doping approach. Additionally, these nitrogen-doped CDs are combined with polyvinyl alcohol (PVA) to formulate secure inks exhibiting solid-state fluorescence and room-temperature phosphorescence (RTP) properties, showcasing their potential for anti-counterfeiting applications in safeguarding important documents and artworks.

Photonic crystal-enhanced fluorescence biosensor with logic gate operation based on one-pot cascade amplification DNA circuit for enzyme-free and ultrasensitive analysis of two microRNAs

The development of sensitive and efficient analytical methods for multiple biomarkers is crucial for cancer screening at early stage. MicroRNAs (miRNAs) are a kind of biomarkers with diagnostic potential for cancer. However, the ultrasensitive and logical analysis of multiple miRNAs with simple operation still faces some challenges. Herein, a photonic crystal (PC)-enhanced fluorescence biosensor with logic gate operation based on one-pot cascade amplification DNA circuit was developed for enzyme-free and ultrasensitive analysis of two cancer-related miRNAs. The fluorescence biosensor was performed by biochemical recognition amplification module (BCRAM) and physical enhancement module (PEM) to achieve logical and sensitive detection. In the BCRAM, one-pot cascade amplification circuit consisted of the upstream parallel entropy-driven circuit (EDC) and the downstream shared catalytic hairpin assembly (CHA). The input of target miRNA would trigger each corresponding EDC, and the parallel EDCs released the same R strand for triggering subsequent CHA; thus, the OR logic gate was obtained with minimization of design and operation. In the PEM, photonic crystal (PC) array was prepared easily for specifically enhancing the fluorescence output from BCRAM by the optical modulation capabilities; meanwhile, the high-throughput signal readout was achieved by microplate analyzer. Benefiting from the integrated advantages of two modules, the proposed biosensor achieved ultrasensitive detection of two miRNAs with easy logic gate operation, obtaining the LODs of 8.6 fM and 6.7 fM under isothermal and enzyme-free conditions. Hence, the biosensor has the advantages of high sensitivity, easy operation, multiplex and high-throughput analysis, showing great potential for cancer screening at early stage.

Probing intracellular potassium dynamics in neurons with the genetically encoded sensor lc-LysM GEPII 1.0 in vitro and in vivo

Neuronal activity is accompanied by a net outflow of potassium ions (K+) from the intra- to the extracellular space. While extracellular [K+] changes during neuronal activity are well characterized, intracellular dynamics have been less well investigated due to lack of respective probes. In the current study we characterized the FRET-based K+ biosensor lc-LysM GEPII 1.0 for its capacity to measure intracellular [K+] changes in primary cultured neurons and in mouse cortical neurons in vivo. We found that lc-LysM GEPII 1.0 can resolve neuronal [K+] decreases in vitro during seizure-like and intense optogenetically evoked activity. [K+] changes during single action potentials could not be recorded. We confirmed these findings in vivo by expressing lc-LysM GEPII 1.0 in mouse cortical neurons and performing 2-photon fluorescence lifetime imaging. We observed an increase in the fluorescence lifetime of lc-LysM GEPII 1.0 during periinfarct depolarizations, which indicates a decrease in intracellular neuronal [K+]. Our findings suggest that lc-LysM GEPII 1.0 can be used to measure large changes in [K+] in neurons in vitro and in vivo but requires optimization to resolve smaller changes as observed during single action potentials.

A cellulose nanocrystal-based dual response of photonic colors and fluorescence for sensitive benzene gas detection

Benzene, as a common volatile organic compound, represents serious risk to human health and environment even at low level concentration. There is an urgent concern on visualized, sensitive and real time detection of benzene gases. Herein, by doping Fe3+ and graphene quantum dots (GQDs), a cellulose nanocrystal (CNC) chiral nematic film was designed with dual response of photonic colors and fluorescence to benzene gas. The chiral nematic CNC/Fe/GQDs film could respond to benzene gas changes by reversible motion. Moreover, chiral nematic film also displays reversible responsive to humidity changes. The resulting CNC/Fe/GQDs chiral nematic film showed excellent response performance at benzene gas concentrations of 0–250 mg/m3. The maximal reflection wavelength film red shifted from 576 to 625 nm. Furthermore, structural color of CNC/Fe/GQDs chiral nematic film change at 44 %, 54 %, 76 %, 87 %, and 99 % relative humidity. Interestingly, due to the stability of GQDs to water molecules, CNC/Fe/GQDs chiral nematic film exhibit fluorescence response to benzene gas even in high humidity (RH = 99 %) environment. Besides, we further developed a smartphone-based response network system for quantitively determinization and signal transformation. This work provides a promising routine to realize a new benzene gas response regime and promotes the development of real-time benzene gas detection.

Determination of kilovoltage x-ray therapy depth doses with open-ended applicators.

The purpose of this work was to determine percentage depth dose (PDD) curves for kilovoltage x-rays from the WOmed-T105 unit, with open-ended steel applicators and beam qualities ranging from 0.5 to 4.2mm Al. Measurements were made with parallel plate chambers in a water phantom, with extrapolation based on a fifth order polynomial used to estimate the surface dose. Measurements were also made with parallel plate chambers in a plastic water phantom, with thin plastic sheets used to obtain detailed measurements at shallow depths (less than 1mm). Monte Carlo simulations were performed using the EGSnrc package, with two different sources as input: a SpekPy simulation of the x-ray beam and a full simulation of the x-ray tube, treatment head and applicators. Results showed that all four methods (two measurements and two simulations) agreed within the measurement uncertainty at depths greater than 2mm. At shallow depths, significant differences were noted. At depths less than 0.1mm, the full Monte Carlo simulation and the solid water measurements showed a sharp spike in surface dose which is attributed to electron contamination, which was not seen in the SpekPy Monte Carlo simulation or the extrapolated water measurements. At depths between 0.1mm and 2mm, beyond the range of contaminant electrons, the extrapolated water measurements underestimate the dose by up to 13% compared to the full Monte Carlo simulation and the solid water measurements, attributed to fluorescent photons generated in the applicators. This work demonstrates that for open-ended applicators, measurement of depth doses in water with extrapolation of surface dose has the potential to significantly underestimate the dose at shallow depths between the surface and 2mm, even after eliminating electron contamination from the beam.

Heralded initialization of charge state and optical-transition frequency of diamond tin-vacancy centers

Diamond tin-vacancy centers have emerged as a promising platform for quantum information science and technology. A key challenge for their use in more-complex quantum experiments and scalable applications is the ability to prepare the center in the desired charge state with the optical transition at a predefined frequency. Here we report on heralding such successful preparation using a combination of laser excitation, photon detection, and real-time logic. We first show that fluorescence photon counts collected during an optimized resonant probe pulse strongly correlate with the subsequent charge state and optical-transition frequency, enabling real-time heralding of the desired state through threshold photon counting. We then implement and apply this heralding technique to photoluminescence-excitation measurements, coherent optical driving, and an optical Ramsey experiment, finding strongly increased optical coherence with increasing threshold. Finally, we demonstrate that the prepared optical frequency follows the probe laser across the inhomogeneous linewidth, enabling tuning of the transition frequency over multiple homogeneous linewidths. Published by the American Physical Society 2024

Fluorescence lifetime of plant leaves with sub-nanosecond resolution

The study aimed to develop a measurement apparatus for in vivo chlorophyll-a (Chl-a) fluorescence decay measurements of plants by means of time correlated single photon counting. In this approach, sub-nanosecond laser pulses with a repetition rate of 10 MHz are applied to excite the sample, followed by the analysis of arrival times of the emitted fluorescence photons. Photon statistics are generated by iteratively fitting the sum of two exponential functions. The tool was tested on both plastid and in vivo leaf samples of Savoy cabbage (Brassica oleracea var. sabauda) with 3–4 subsequent leaves giving a complete sample coverage starting from the outermost. The Chl-a fluorescence lifetime exhibited a gradual increase in both the isolated plastid suspensions and the in vivo leaf samples towards the innermost leaf layers explained by an increase of natural absence of light (etiolation syndrome). Furthermore, cadmium stress and iron deficiency were investigated on treated sugar beet (Beta vulgaris) samples in vivo using TCSPS measurements. The reduced fluorescence quenching resulted in an increased fluorescence lifetime. Finally, a long-term (10 week) testing of the setup was carried out on Chl-retaining resurrection Haberlea rhodopensis plants protecting themselves by an elevated non-photochemical quenching yielding a decrease of fluorescence lifetime during their desiccation.

Revealing degradation mechanisms of archaeological flax textiles through the evolution of fibres’ parietal polymers by synchrotron deep-UV fluorescence

Autofluorescence generated by plant cells and tissues provides a label-free method for investigating them without altering their structure and biochemistry. While in the literature, research mainly focuses on investigating fresh plant tissues, this study examines flax yarns from five archaeological artefacts to understand how cell wall fibres degrade and how their biochemical composition is modified after natural ageing over millennia. Using Synchrotron-based deep UV fluorescence (S-DUV), we aim to correlate fibre autofluorescence with the environmental conditions of discovery (clothes of votive statuettes buried in a sanctuary or shrouds and bandages for mummification rituals found in tombs) or their intended purposes (fishing net, which underwent wet-dry cycles during its use). Out of the five archaeological objects studied, the two yarns sampled from the buried fabrics were found encrusted with minerals, but with significant differences in the fibres’ degradation. The yarn sampled from the fishing net displayed a great variability of the dataset, with some fibres biochemically similar to the buried samples while others were closer to the funerary linen shrouds. Lignin's predominant presence at 480 nm in the fishing net suggests extensive cellulose-enriched cell wall layer degradation while the lignin-enriched layer is still preserved. Additionally, second harmonic generation imaging microscopy (SHG) and 2-photon excitation fluorescence (2PEF) were used alongside S-DUV analyses to evaluate the flax fibres’ ultrastructure. SHG confirmed S-DUV findings and indicated poor crystalline cellulose preservation in one linen shroud, explaining the yarn's brittleness.

A novel photonic crystal hydrogel inverse opal fluorescence enhancement platform for highly sensitive immunoassay of tumor markers

Cancer is a significant global health issue, necessitating early detection for effective diagnosis and treatment. We presented a novel method for detecting tumor markers using fluorescence-enhanced photonic crystal hydrogel inverse opal (PC-GELIO) membranes. We efficiently fabricated large-area, low-crack photonic crystal membranes using a homemade microfluidic chip. Composed of PEG-DA and PEG, the hydrogel replicated the photonic crystal structure, yielding photonic crystal hydrogel inverse opal membranes with a unique photonic band gap and inverse opal porous structure. These properties afford the PC-GELIO platform several advantages: Firstly, the high stability of the internal nanostructure in the large-area, low-crack photonic crystals film, prepared using the homemade microfluidic chip, is crucial for preserving the platform's exceptional fluorescence-enhanced sensing capabilities. Secondly, the peak wavelength emitted by fluorescent molecules aligns with the photonic band gap (PBG), significantly enhancing the fluorescence signal through the low-photon effect. Lastly, the high specific surface area provides numerous binding targets for biomolecule modification, and the hydrogel offers a uniform liquid environment conducive to biomolecule binding. We evaluated the fluorescence-enhanced sensing performance of the platform using alpha-fetoprotein (AFP). The limit of quantification (LOQ) for AFP was determined to be as low as 23 pg/mL, representing an order of magnitude improvement compared to non-enhanced platforms (0.29 ng/mL and 0.25 ng/mL). Consequently, this novel fluorescence-enhanced photonic crystal hydrogel inverse opal platform holds significant potential as a straightforward and efficient method for biomolecular detection.

Detection of recurrent fluorescence from anthracene using an electrostatic ion beam trap

The recurrent fluorescence of anthracene cations (C14H10+) was investigated using an electrostatic ion beam trap. The photon emission from the excited anthracene cations confined in the trap was observed in the order of milliseconds. The photon yields as a function of the wavelength in the range of 450–860 nm were measured by optical filters and a cooled photomultiplier, which revealed that the observed photon emission is attributed to the D2 → D0 transition of C14H10+. However, the time range of the photon emission is considerably longer than that of the spontaneous emission induced by the D2 → D0 transition (<1 μs). The number of photons emitted by the recurrent fluorescence of C14H10+ as a function of time was calculated using the previously reported theoretical decay rates of C14H10+ by recurrent fluorescence and thermal dissociation. The calculation results justified the time dependence of the measured number of photons over the extended time range. These results demonstrate that we successfully detected recurrent fluorescence photons emitted from excited anthracene cations.