Ultraviolet Light Source Research Articles

Data-driven modeling of the thermal dynamics of a dual-spectral ultraviolet sterilizer and control of the output irradiance

Multi-channel LED light sources possess complicated nonlinear photo-electro-thermal (PET) dynamics. Modeling such PET dynamics is challenging, but important to ensure the performance of these light sources. Traditional first-principle modeling methods that have been reported in the literature yield either single-channel LED dynamic models, or multi-channel static models. On the other hand, system identification (SID) methods have also been applied, and lead to both single-channel nonlinear dynamic models and multi-channel linear time invariant (LTI) models. However, there are still few attempts given to build multiple-input-multiple-output (MIMO) nonlinear dynamic models of multi-channel LED systems. In this work, we try to model the PET dynamics of a dual-spectral ultraviolet (UV) light source, with a structured nonlinear system identification technique, i.e., linear parameter varying (LPV) SID technique. The experimental prototype contains a 280 nm UVC channel and a 365 nm UVA channel, respectively driven by two separate constant current sources, and is hence a MIMO system. Its nonlinear electro-thermal model is first identified from experimental data by the LPV-SID method, which is then integrated with the estimated photo-electro model to form a complete PET dynamic model. The experimental results have verified that the model can accurately predict the temperature variations at two representative points on the LED board. Moreover, the identified model has been applied in designing a feedforward-feedback controller to precisely track the reference radiation levels of the two UV channels, despite the strong nonlinearity caused by both the electro-thermal dynamics and the temperature-dependent lumen efficacy.

High power light source for future extreme ultraviolet lithography based on energy-recovery linac free-electron laser

The development of ways to increase the intensity of extreme ultraviolet (EUV) light sources for future EUV lithography is important to realize high throughput fine patterning. The energy-recovery linac (ERL) free-electron laser (FEL), which is an accelerator based light source, is a candidate for this. We clarify the design concept of the ERL-FEL for EUV light sources for future lithography, delivery systems of the FEL light to multiscanners, and future development items of the accelerator technologies and a possibility of the beyond EUV.

Water-based combifuge ink with unique tamper-evident features for anti-counterfeiting applications

Unique characteristics of pigments in printing inks are essential in achieving multi-level security features in genuine articles to combat counterfeiting. This study reports the synthesis and characterisation of 6-bromo-5-hydroxy-2-(2-hydroxyethyl)-1H-benzo[de]isoquinoline-1,3(2H)-dione (BHENA) as a biocompatible and thermally stable pigment with attractive features for anti-counterfeiting application. A water-based stable ink was formulated using BHENA pigment and printed on security paper using flexography technique. The homogeneous pale-yellow print dried fast, and displayed good rub-resistance as well as light-fastness. The print proofs demonstrated captivating fluorescence responses upon exposure to different solvents and sodium hydroxide, when viewed under 365 nm ultraviolet (UV) light source, which could provide clear evidence for document tampering. Moreover, a remarkable penetrating fluorescence that show through the rear side of the print can be a novel add-on security feature. The combifuge eco-friendly luminescent ink can thus impart robust tamper-evident security features, especially penetrating UV fluorescence even with minimal pigment concentration, in cheques, legal or confidential documents, certificates, merchandise and electronic barcodes to avoid duplication or sale of fake products. Further, the electrical features and surface morphology analysis of the prints advocate the suitability of formulated water-based ink to achieve low-voltage-driven organic thin-film transistors on security documents and banknotes for anti-forgery applications. Furthermore, an ultra-high frequency organic- Radio frequency identification antenna resonating at 1.03 GHz has been designed and simulated as yet another anti-counterfeiting solution. The antenna has the advantage of compact size, better impedance matching and suitable radiation characteristics, thereby making it as a very competitive candidate for appropriate applications.

Which UV wavelength is the most effective for chlorine-resistant bacteria in terms of the impact of activity, cell membrane and DNA?

The widespread use of chlorine disinfectants in drinking water has accelerated the selection of chlorine-resistant bacteria (CRB). The presence of CRB in drinking water (during treatment, distribution, and consumption) has a profound impact on public safety. Ultraviolet (UV) irradiation is an effective control technology for CRB. Nevertheless, the relative efficacies of different UV light wavelengths (traditional mercury lamps, ultraviolet light-emitting diodes (UV-LED 265 nm and 285 nm), and 222 nm krypton-chlorine excilamps) in the control and inactivation of various CRB have not been investigated. In this study, the impacts of different UV light sources on the inactivation rate and microbial cell structure of CRB were evaluated. The results showed that the order of inactivation efficacy was as follows: UV-LED 265 nm > low-pressure ultraviolet (LPUV) ≈ medium-pressure ultraviolet (MPUV) ≈ 222 nm > UV-LED 285 nm. CRB was inactivated via DNA damage and additional ATP decline under UV-LED 265 nm, UV-LED 285 nm and LPUV irradiation, of which UV-LED 265 nm was the most effective based on fluence and inactivation rate constants. The inactivation mechanisms revealed that the 222 nm wavelength was significantly different from other wavelengths; it stimulated the production of a large number of reactive oxygen species (ROS) which resulted in bacterial cell membrane damage, ATP direct decline, and a small number of DNA lesions. Multispectral MPUV induced both of the foregoing mechanisms but mainly damaged DNA. The present study provides empirical evidence for the reasonable application of UV disinfection technology in the treatment of water and wastewater and their conduits and delivery systems.

Long persistent luminescence property of green emitting Sr3Ga4O9: Tb3+ phosphor for anti-counterfeiting application

In this work, a long persistent luminescent (LPL) material Sr3Ga4O9:Tb3+ is synthesized via a high-temperature solid-state reaction. The crystal structure, luminescence properties, decay curves and thermoluminescence (TL) curves of Sr3Ga4O9:Tb3+ are studied in detail. When the ultraviolet (UV) light source was turned off, Sr3Ga4O9:Tb3+ phosphor exhibit typical LPL behavior for approximately 7.5 h. The obtained results indicated that the green long persistent emitting was similar to the photoluminescence (PL), originated form the typical 5D4→7F5 transition of Tb3+ ions. We propose the persistent luminescence mechanism of Tb3+ doped Sr3Ga4O9. Electrons in the conduction band and holes in the valence band form stable excitons, and it can play an important role in energy transfer. Based on the specific characteristics of the phosphor, a dual-mode luminescence image is fabricated for application in anti-counterfeiting.

An Improved U-Net Segmentation Model That Integrates a Dual Attention Mechanism and a Residual Network for Transformer Oil Leakage Detection

Accurately detecting oil leakage from a power transformer is important to maintain its normal operation. Deep learning (DL) methods have achieved satisfactory performance in automatic oil detection, but challenges remain due to the small amount of training data and oil targets with large variations in position, shape, and scale. To manage these issues, we propose a dual attention residual U-net (DAttRes-Unet) within a U-net architecture that extensively uses a residual network as well as spatial and channel-wise attention modules. To overcome the vanishing gradient problem due to deeper layers and a small amount of training data, a residual module from ResNet18 is used to construct the encoder path in the U-net framework. Meanwhile, to overcome the issue of training difficulty for the network, inspired by the advantage of transfer learning, initial network parameters in the encoder are obtained from the pre-trained ResNet18 on the ImageNet dataset. Further, in the decoder path, spatial attention and channel attention are integrated to highlight oil-stained regions while suppressing the background or irrelevant parts/channels. To facilitate the acquisition of the fluorescence images of the transformer, we designed a portable acquisition device integrating an ultraviolet light source and a digital camera. The proposed network is trained on the amount of fluorescence images after data augmentation is used and tested on actual fluorescence images. The experiment results show that the proposed DAttRes-Unet network can recognize oil-stained regions with a high accuracy of 98.49% for various shapes and scales of oil leakage.

The development of the alarm system for HLS-II

Hefei Light Source II (HLS-II) is a vacuum ultraviolet synchrotron light source. The control system of HLS-II is a distributed system based on the experimental physics and industrial control system (EPICS). The alarm system of HLS-II is responsible for monitoring the alarm state of the facility and distributing the alarm message in time. It facilitates the operator to troubleshoot problem efficiently, so as to improve the availability of HLS-II. Phoebus/Alarms (Alarms) is the latest alarm software released in EPICS community. Based on Alarms, the alarm system of HLS-II is designed, developed and deployed. The alarm distribution strategy is designed from the perspective of the HLS-II operation mode, alarm severity and alarm representative to overcome alarm floods. The 3 ways to distribute the alarm message are added to the HLS-II alarm system, which include WeChat, SMS and web-based GUI. In order to configure alarm options efficiently and conveniently, an alarm configuration management tool is developed based on the MySQL database and Browser/Server architecture. The alarm system of HLS-II has been deployed since November 2021. The result indicates that the alarm system is effective and convenient to operate.

Rotational state specific dissociation dynamics of D2O via the C̃(010) state: The effect of bending vibrational excitation.

The rotational state resolved photodissociation dynamics of D2O via the C̃(010) state has been investigated by using the D-atom Rydberg tagging time-of-flight technique combined with a tunable vacuum ultraviolet light source. The D-atom action spectrum of the C̃(010) ← X̃(000) band and the corresponding time-of-flight (TOF) spectra of D-atom photoproducts formed following the excitation of D2O to individual rotational transition have been measured. By comparison with the action spectrum of the C̃(000) ← X̃(000) band, the bending vibrational constant of the C̃ state for D2O can be determined to be v2 = 1041.37 ± 0.71cm-1. From the TOF spectra, the product kinetic energy spectra, the vibrational state distributions of OD products, and the state resolved anisotropy parameters have been determined. The experimental results indicate a dramatic variation in the OD product state distributions for different rotational excitations. This illuminates that there are two distinctive coupling channels from the C̃(010) state to the low-lying electronic states: the homogeneous electronic coupling to the Ã1B1 state, resulting in vibrationally hot OD(X) products, and the Coriolis-type coupling to the B̃1A1 state, producing vibrationally cold but rotationally hot OD(X) and OD(A) products. Furthermore, the three-body dissociation channel is confirmed, which is attributed to the C̃ → 1A2 or C̃ → Ã pathway. In comparison with the previous results of D2O photolysis via the C̃(000) state, it is found that the v2 vibration of the parent molecule enhances both the vibrational and rotational excitations of OD products.

Ultraviolet actinometry – Determination of the incident photon flux and quantum yields for photochemical systems using low-pressure and ultraviolet light-emitting diode light sources

The study of the interaction of light with photochemical and photobiological systems requires an accurate assessment of the incident photon flux. The determination of photon fluxes for various light sources (monochromatic and polychromatic) has an inherent advantage since the use of standard quantum yields for the actinometer assures that the photon flux has been calculated against accepted standards. Alternatively, if the photon flux is known, chemical actinometry can be used to determine quantum yields. This study illustrates how incident photon fluxes and quantum yields can be estimated for photochemical and photobiological systems. First, an example is developed to calibrate a spectroradiometer using a low-pressure (LP) UV lamp using either the ferrioxalate or iodide/iodate actinometers. The Calibration Factors (CFs) (defined as the ratio between the actinometer and the spectroradiometer) agreed very well, demonstrating the consistency of quantum yields between well-researched actinometers. Second, since UV-LEDs have a bandwidth almost twice that of LP lamps, should UV-LEDs be treated as monochromatic or polychromatic light sources? Results showed no significant differences between the monochromatic analysis and the polychromatic analysis. Third, the uridine quantum yield is 0.025 ± 0.001 over the 254–279 nm wavelength range, independent of these wavelengths.

Following the Light: Use of Multimodal Imaging and Fiber Optic Spectroscopy to Evaluate Aging in Daylight Fluorescent Artists’ Pigments

Daylight fluorescent artists’ colors have been well established as fugitive. Upon exposure to light, these vibrant colors can fade and exhibit color shifts. Artwork containing these fluorescent colorants presents complex challenges for art conservators faced with conserving these inherently problematic materials. This paper examined nine fluorescent colorants obtained from Kremer Pigmente, referred to the previous literature and research, and attempted to quantify the visual and photographic observations of fading and color changes. It provides additional information that could be useful in considering conservation documentation and treatment. Fiber optic spectroscopy using ultraviolet and visible light sources was used to measure the spectral shifts of the colorants before and after exposure to light. The fluorescent colors exhibited alterations in intensity coupled with primary peak shifts in the spectrum corresponding to the optical fading and color shifts. Multimodal imaging was executed to analyze the pigments in different regions of the spectrum before and after aging, which has not been documented before with these fluorescent colorants. Imaging in various regions of the spectrum indicated differences in absorption and reflectance between the pigments as captured by a modified camera. The results were compared to recently published research including the identification of the dyes present in the Kremer line of pigments. Multimodal imaging and fiber optic spectroscopy provided valuable information for future documentation and conservation of artworks containing these colorants. Specifically, these non-invasive techniques provide a method to document and identify the spectral changes between the aged and unaged pigment, graph and predict the direction of overall color change, and provide useful data for establishing future conservation treatment protocols.

Role of Shift Vector in High-Harmonic Generation from Noncentrosymmetric Topological Insulators under Strong Laser Fields

As a promising avenue to obtain new extreme ultraviolet light source and detect electronic properties, high-harmonic generation (HHG) has been actively developed in both theory and experiment. In solids lacking inversion symmetry, when electrons undergo a nonadiabatic transition, a directional charge shift occurs and is characterized by shift vector, which measures the real-space shift of the photoexcited electron and hole. For the first time, we have revealed that shift vector plays prominent roles in the real-space tunneling mechanism of three-step model for electrons under strong laser fields. Since shift vector is determined by the topological properties of related wave functions, we expect HHG with its contribution can provide direct knowledge on the band topology in noncentrosymmetric topological insulators (TIs). In both Kane-Mele model and realistic material BiTeI, we have found that the shift vector reverses when band inversion happens during the topological phase transition between normal and topological insulators. Under oscillating strong laser fields, the reversal of shift vector leads to completely opposite radiation time of high-order harmonics. This makes HHG a feasible all-optical strong-field method to directly identify the band inversion in non-centrosymmetric TIs.

Development of a pulsed vacuum ultraviolet light source with adjustable intensity.

This paper describes the development of a pulsed light source using the discharge from an electrode in a medium of various noble gases. This source can be used to aid in the characterization and testing of new vacuum-ultraviolet sensitive light detection devices. The source includes a novel spark driver circuit, a spark chamber into which different noble gases can be introduced, and an optical attenuation cell capable of being filled with different gases to allow for the attenuation of the pulsed light down to single photon levels. We describe the construction, calibration, and characterization of this device deployed at a dedicated light detection test stand at Oak Ridge National Laboratory.

Nano-photocatalytic Mineralization and Degradation of Dye Acid Orange 7 on Titanium Dioxide Coated Layers in a Batch Mode Plate Photo Reactor: Role of Flow Rate and Inorganic Salts

Recently, the environmental impact of discharged untreated dye wastewater has received extensive attention. Herein, the paper investigated the photocatalytic degradation of dye Acid Orange 7 in a batch mode photoreactor fitted with a TiO2 coated layer of dimensions (10cmí—15cm). The coated layer was prepared by sedimentation from an aqueous suspension of c=5 g.L-1 and annealed at 300°C. Polychromatic sun beds lamps were used as a source of Ultra Violet (UV) light with maximum intensity at λ= 365 nm. A UV-Vis spectrophotometer monitored changes in dye concentrations at = 485 nm. Photocatalytic degradation of dye Acid Orange 7; c= (2.5í—10-5 mol. L-1) was determined by changes in dye concentration under UV light irradiation. The results show that dyes can be effectively degraded by TiO2photocatalyst and UV light of wavelength 300-400 nm. The effect of flow rate and inorganic salts (sodium carbonate, sodium sulfate) on dye Acid Orange 7 degradation was examined. The maximum absorption wavelength and maximum coefficient of molar absorptivity ) was determined at 485 nm and 20647 dm3.mol-1.cm-1. The presence of CO32- ions in the dye solution accelerated photocatalytic degradation by 35.8% and 39.3% after 30 minutes and 60 minutes of photocatalytic degradation. Dye photodegradation was reduced by 76.4% after 2.5 hours of photocatalytic treatment with SO42- ions dissolved in dye solution. Presence of SO42-ions showed no effect. Additionally, a flow rate of 50 lit/hr. was effective by 85.1% compared to 100 lit/hr. after 4 hours of photocatalytic degradation.

AC‐Driven Ultraviolet‐C Electroluminescence from an All‐Solution‐Processed CaSiO3:Pr3+ Thin Film Based on a Metal‐Oxide‐Semiconductor Structure

AbstractAn ultraviolet (UV) light source is continuously required for applications of sterilization as well as industrial value. In particular, research on materials and devices emitting UV‐C radiation in the range from 210 to 280 nm is very meaningful and challenging work. Herein, UV‐C electroluminescence (EL) from an all‐solution processed CaSiO3:Pr3+ (CSO) thin film is reported for the first time. The CSO thin film is formed on a Si substrate (size of 13 × 13 mm2), and structurally, the UV‐C EL device has a metal‐oxide‐semiconductor (MOS) shape consisting of CSO and interlayered SiOx of 100 and 150 nm thickness, respectively, on Si. The emission and electrical properties of the UV‐C EL device are investigated under an alternating current system. The results reveal UV‐C emission peaking at 276 nm attributed to the 4f5d‐3H(F)j transition of Pr3+ ions within CSO, with a maximum output optical power of 8.37 µW cm−2 (power efficiency of 0.15%) at an operating voltage of 40 Vop (50 Hz). The work can provide a feasible method for realizing large‐area UV‐C‐emitting devices based on the MOS structure.

Rate of Photocatalytic Degradation of Acid Orange 7 Azo Dye on TiO2 Coated Layers: Role of pH and Initial Dye Concentration

This paper examined the role of pH and initial dye concentration on the rate of Acid Orange 7 photocatalytic degradation. A batch mode plate photocatalytic reactor fitted with a TiO2 coated layer of dimensions (10cm×15cm) immobilized on microscopic glass was used. The coated layer was prepared by sedimentation from an aqueous suspension of 5 g.L-1 phase and annealed at 300°C. Polychromatic sun beds lamps were used as a source of Ultra Violet (UV) light with maximum intensity at wavelength λ= 365 nm. An appropriate dye solution flow rate of 50 lit/hr was used. A UV-Vis spectrophotometer monitored changes in dye concentrations at λ_max= 485 nm. From changes in dye concentration during irradiation the rate of photocatalytic degradation was determined. The findings reveal that pH range 5 to 9 the degradation rate is almost constant, for pH values lower than 5 it marginally increases while for pH values above 9 it significantly decreases. Additionally the degradation rate increased significantly with increasing initial dye concentration in the range from (1×10-5 mol.L-1 to 8×10-5 mol. L-1). The amount of adsorbed Acid Orange 7 increases with increased dye concentration, however for concentrations greater than 1×10-4 mol. L-1 it was observed that the increase was marginal. The findings confirm a direct correlation between the amount of dye adsorbed and resultant degradation rate. The optimum pH and initial dye concentration were determined ;[( pH= 3, r=1.6×10-7 mol.m-2.s-1); (initial concentration = 8×10-5 mol.L-1 to 1×10-4 mol.L-1, r= 3×10-7 mol.m-2.s-1)]. A shift in dye solution pH from acidic to basic in the range 3 to 11.5 reduced photocatalytic degradation rates by 56.3%.

Ultraviolet C random lasing at 230–280 nm from Pr3+ doped bulk crystal resonators by two-photon absorption

Ultraviolet solid-state light sources, especially in the short-wave ultraviolet band, are attracting great attention for potential applications in high-density optical data storage, biomedical research, and water and air purification and sterilization. As one of the means to generate solid-state short-wavelength lasers, upconversion technology, which can transform a low-energy photon to a high-energy photon, has a simple structure and does not require strict phase-matching conditions. However, because of the high non-radiative decay rate during multiphoton absorption process, the short-wave upconversion ultraviolet lasing is still difficult to achieve. Here, under 450 nm blue laser excitation, we have successfully obtained ultraviolet C random lasing from a Pr3+ doped YPO4 single crystal via two-photon absorption. Presently, ultraviolet C random lasing with the wavelength range of 230–280 nm is the shortest wavelength for upconversion lasing emission.

Preparation and performance of photocatalytic NO degradation superhydrophobic coatings for tunnel.

Due to the semi-closed structure of the tunnel, serious air pollution in tunnels from vehicle exhaust becomes an issue which needed to be addressed. Among the exhaust, nitric oxide (NO) is typically considered as one of the main pollutants. In this paper, a superhydrophobic photocatalytic coating was fabricated by a spraying method by airbrush with a WO3/TiO2 photocatalysis for NO degradation. The water advanced contact angle (WACA) of the coating reached 166.32°, and the WACA was still above 145° after the 30 times abrasion test. The coating exhibited an excellent ability to remove inorganic and organic pollutants. Also, the NO degradation efficiency of this superhydrophobic coating under ultraviolet and visible light sources and humid environments was tested. When the relative humidity reached 98%, the NO degradation efficiency of the coating remained unchanged under visible light irradiation compared with the relative humidity of 45%. In addition, the coating exhibited prominent stability of NO degradation during the cyclic test. Furthermore, the WT coating showed stability and synergy of self-cleaning and photocatalysis toward NO degradation, which ensured the long-term use of the coating. Finally, a synergistic mechanism for self-cleaning and photocatalysis was proposed. This may provide a new idea and support for the application of photocatalytic technology in the degradation of NO in the tunnel.

Extreme Ultraviolet Reflection-Absorption Spectroscopy: Probing Dynamics at Surfaces from a Molecular Perspective.

Extreme ultraviolet light sources based on high harmonic generation are enabling the development of novel spectroscopic methods to help advance the frontiers of ultrafast science and technology. In this Account, we discuss the development of extreme ultraviolet reflection-absorption (XUV-RA) spectroscopy at near grazing incident reflection geometry and highlight recent applications of this method to study ultrafast electron dynamics at surfaces. Measuring core-to-valence transitions with broadband, femtosecond pulses of XUV light extends the benefits of X-ray absorption spectroscopy to a laboratory tabletop by providing a chemical fingerprint of materials, including the ability to resolve individual elements with sensitivity to oxidation state, spin state, carrier polarity, and coordination geometry. Combining this chemical state sensitivity with femtosecond time resolution provides new insight into the material properties that govern charge carrier dynamics in complex materials. It is well-known that surface dynamics differ significantly from equivalent processes in bulk materials and that charge separation, trapping, transport, and recombination occurring uniquely at surfaces govern the efficiency of numerous technologically relevant processes spanning photocatalysis, photovoltaics, and information storage and processing. Importantly, XUV-RA spectroscopy at near grazing angle is also surface sensitive with a probe depth of ∼3 nm, providing a new window into electronic and structural dynamics at surfaces and interfaces. Here we highlight the unique capabilities and recent applications of XUV-RA spectroscopy to study photoinduced surface dynamics in metal oxide semiconductors, including photocatalytic oxides (Fe2O3, Co3O4 NiO, and CuFeO2) as well as photoswitchable magnetic oxide (CoFe2O4). We first compare the ultrafast electron self-trapping rates via small polaron formation at the surface and bulk of Fe2O3 where we note that the energetics and kinetics of this process differ significantly at the surface. Additionally, we demonstrate the ability to systematically tune this kinetics by molecular functionalization, thereby providing a route to control carrier transport at surfaces. We also measure the spectral signatures of charge transfer excitons with site specific localization of both electrons and holes in a series of transition metal oxide semiconductors (Fe2O3, NiO, Co3O4). The presence of valence band holes probed at the oxygen L1-edge confirms a direct relationship between the metal-oxygen bond covalency and water oxidation efficiency. For a mixed metal oxide CuFeO2 in the layered delafossite structure, XUV-RA reveals that the sub-picosecond hole thermalization from O 2p to Cu 3d states of CuFeO2 leads to the spatial separation of electrons and holes, resulting in exceptional photocatalytic performance for H2 evolution and CO2 reduction of this material. Finally, we provide an example to show the ability of XUV-RA to probe spin state specific dynamics in a photoswitchable ferrimagnet, cobalt ferrite (CoFe2O4). This study provides a detailed understating of ultrafast spin switching in a complex magnetic material with site-specific resolution. In summary, the applications of XUV-RA spectroscopy demonstrated here illustrate the current abilities and future promise of this method to extend molecule-level understanding from well-defined photochemical complexes to complex materials so that charge and spin dynamics at surfaces can be tuned with the precision of molecular photochemistry.

Cut-flower Carnation Photoluminescence: Potential New Value-added Product

Success of the floral industry lies in strengthening the fresh flower market with value-added products. An experiment was conducted to quantify luminescence of cut-flower white carnations after exposure to two fluorescent products (dye from a yellow highlighter or glow-in-the-dark spray paint). Single stems were placed in bud vases that were filled with 240 mL deionized water and 2 g floral preservative. Highlighter treatments were applied to the vase as either one drop, three drops, or half of the dye reservoir (half stick). Paint treatments were applied at 2-, 4-, or 6-second durations to the flowers. Combination treatments were applied as three drops of highlighter dye plus either 2, 4, or 6 seconds of paint application. Treatments were compared against each other and a nontreated control. There were five repetitions of three stems per treatment arranged in a completely randomized design. Measurements were taken daily on stem fresh weight, flower diameter, quality rating, flower maximum brightness, flower mean brightness, relative stem fresh weight percentage, overall solution absorption rate percentage, and daily solution absorption rate. Stem fresh weight, relative stem fresh weight percentage, flower diameter, and overall solution absorption rate were greatest on day 4. Flower maximum brightness without ultraviolet (UV) light was greatest 2 days after treatment (DAT), but still produced a detectable glow through 8 DAT. Among treatments before UV charge, the 6-second paint duration provided the greatest flower maximum brightness value. The half-stick highlighter treatment had the greatest vase mean brightness. All paint treatments reduced flower quality. For each treated flower, the UV charge increased the brightness values, which ranged from 53% to 206% greater than before the UV charge. White carnations can luminesce with spray applications of glow-in-the-dark spray paint or through the stem absorption method using yellow highlighter dye, with the latter being less detrimental to vase life but requiring a UV light source to glow.

A narrow bandwidth extreme ultra-violet light source for time- and angle-resolved photoemission spectroscopy.

Here, we present a high repetition rate, narrow bandwidth, extreme ultraviolet photon source for time- and angle-resolved photoemission spectroscopy. The narrow bandwidth pulses meV for photon energies eV are generated through high harmonic generation using ultra-violet drive pulses with relatively long pulse lengths (461 fs). The high harmonic generation setup employs an annular drive beam in tight focusing geometry at a repetition rate of 250 kHz. Photon energy selection is provided by a series of selectable multilayer bandpass mirrors and thin film filters, thus avoiding any time broadening introduced by single grating monochromators. A two stage optical-parametric amplifier provides < 100 fs tunable pump pulses from 0.65 μm to 9 μm. The narrow bandwidth performance of the light source is demonstrated through angle-resolved photoemission measurements on a series of quantum materials, including high-temperature superconductor Bi-2212, WSe2, and graphene.