Absolute Intensity Measurements Research Articles

Measurement of the zodiacal light absolute intensity through Fraunhofer line spectroscopy of the night sky with the Hale telescope

Abstract Measuring the absolute brightness of the zodiacal light (ZL), which is the sunlight scattered by interplanetary dust particles, is important not only for understanding the physical properties of the dust but also for constraining the extragalactic background light (EBL) by subtracting the ZL foreground. We describe the results of high-resolution spectroscopic observations of the night sky in the wavelength range of 300–900 nm with the double spectrograph on the Hale telescope to determine the absolute brightness of the ZL continuum spectra from the Fraunhofer absorption line intensities. The observed fields are part of the fields observed by the Spitzer Space Telescope for the EBL study. Assuming that the spectral shape of the zodiacal light is identical to the solar spectrum in a narrow region around the Fraunhofer lines, we decomposed the observed sky brightness into multiple emission components by amplitude parameter fitting with spectral templates of the airglow, ZL, diffuse Galactic light, integrated starlight, and other isotropic components including EBL. As a result, the ZL component with the Ca ii λλ 393.3, 396.8 nm Fraunhofer lines around 400 nm is clearly separated from the others in all fields with uncertainties around 20%, mainly due to the template errors and the time variability of the airglow. The observed ZL brightness in most of the observed fields is consistent with the modeled ZL brightness calculated by combining the most conventional ZL model at 1250 nm based on the Diffuse Infrared Background Experiment and the observational ZL template spectrum based on the Hubble Space Telescope. However, the ecliptic plane observation is considerably fainter than the ZL model, and this discrepancy is discussed in terms of the optical properties of the interplanetary dust accreted in the ecliptic plane.

Fit-free analysis of fluorescence lifetime imaging data using chemometrics approach for rapid and nondestructive wood species classification

Abstract Conventional fluorescence spectroscopy has been suggested as a valuable tool for classifying wood species rapidly and non-destructively. However, because it is challenging to conduct absolute emission intensity measurements, fluorescence analysis statistics are difficult to obtain. In this study, another dimension of fluorescence, that is, fluorescence lifetime, was further evaluated to address this issue. A time-resolved fluorescence spectroscopic measurement system was first designed, mainly using a streak camera, picosecond pulsed laser at 403 nm, and a spectroscope, to collect the fluorescence time-delay (FTD) profiles and steady-state fluorescence intensity (FI) spectra simultaneously from 15 wood species. For data analysis, principal component analysis was used to “compress” the mean-centered FTD and FI spectra. Then, support vector machine classification analysis was utilized to train the wood species classification model based on their principal component scores. To avoid overfitting, ten-fold cross-validation was used to train the calibration model using 70 % of the total samples, and the remaining 30 % hold-out validation was used to test its reproducibility. The cross-validation accuracies were 100 % (5 softwoods) and 96 % (10 hardwoods), with test-validation accuracies of 96 % and 89 %.

Infrared spectra and optical constants of astronomical ices: V. cyclopropane and ethylene oxide

Infrared (IR) spectra of solid cyclopropane (c-C3H6) and ethylene oxide (c-C2H4O), two cyclic aliphatic compounds, have been recorded in their amorphous and crystalline states. The spectra have been combined with measurements of density and refractive index (λ = 670 nm) for each form of each solid to compute IR intensities (i.e., absorption coefficients and band strengths) and optical constants for use in laboratory experiments and astronomical observations. These are the first such measurements of absolute IR intensities and optical constants for each solid at temperatures relevant to the outer Solar System and the interstellar medium, with all results coming from a single laboratory. Two literature band strengths for ethylene oxide's strongest IR feature, one value a calculation and the other a gas-phase measurement, need to be increased by ∼25% to match the solid-phase value reported here. Suggestions are made for applications and future work related to the chemistry of icy bodies in the Solar System and beyond, including Pluto's surface, Titan's atmosphere, and the formation of cometary C3.

A series of caged fluorophores for calibrating light intensity

A series of hydrophilic and hydrophobic caged-fluorophores have been produced on the pyranine backbone. They are employed for absolute quantification of light intensity of single- or two-photon excitation sources in chemical and biological samples.

Scattered-light uniformity imager for diagnosing laser absorption asymmetries on OMEGA.

Light scattered from a target is the most-direct measurement for diagnosing laser absorption in a direct-drive implosion. Observations from OMEGA implosions show much larger scattered-light asymmetries than predictions. A new instrument has been developed to absolutely measure the scattered-light intensity and nonuniformity for the purpose of diagnosing the asymmetry. The scattered-light uniformity imager (SLUI) diagnostic records the variation in scattered-light intensity over a transmission diffuser using a charge-coupled device (CCD)/lens assembly. At the standard operating position, an 11.3° (f/2.5) cone of light is collected. A stray light baffle, debris shield, and antireflection absorbing filter are also incorporated into the diagnostic payload inserted into the target chamber. The imaging parts of the diagnostic (light baffle, vacuum window, filters, lens, and CCD camera) are located outside the target chamber. Five SLUIs have been built and deployed in OMEGA's ten-inch manipulator diagnostic ports, covering almost 5% of the emission surface, enabling an absolute scattered-light measurement should be within a few percent of the global average. Each SLUI system is calibrated offline, providing absolute scattered-light intensity measurements. Based on the measured point spread function, each diffuser plate image contains over 20 000 independent scattered-light absolute-intensity measurements of the variation over the collection cone. SLUI provides a platform to study scattered light and absorption asymmetries, and their possible sources.

Realizing Simultaneous X‐Ray Imaging and Dosimetry Using Phosphor‐Based Detectors with High Memory Stability and Convenient Readout Process

AbstractFlexible X‐ray storage phosphor sheets are regarded as promising alternatives to conventional electronic flat‐panel X‐ray detectors, enabling X‐ray imaging and dosimetry in less accessible situations. However, it is a challenge to develop phosphor‐based detectors with high memory stability and convenient readout processes. Here, an approach to realize this using radiation‐induced photoluminescence tuning in (Ba1‐xSrx)2SiO4:Eu phosphors is demonstrated, ascribed to the reduction of Eu3+ toward Eu2+. The associated photoluminescence spectral change and the accompanying color contrast in response to the radiation dose are exploited for simultaneous X‐ray dosimetry and imaging. The recorded image can be read out conveniently by a regular photo camera upon UV illumination and the radiation dose can be extracted during the imaging process in a ratiometric way via the green to red pixel intensity, avoiding the need for absolute intensity measurement. Moreover, the imaged information can be maintained for longer than 28 days and the plate can be reused for X‐ray detection after bleaching upon 420 nm illumination, exhibiting superior memory retention ability and good cycling resistance. These results reveal the great potential of (Ba1‐xSrx)2SiO4:Eu for X‐ray‐based microbeam radiation therapy and nondestructive inspection and are expected to stimulate research on phosphor‐based photoluminescence modulated detectors.

Inferred Measurements of the Zodiacal Light Absolute Intensity through Fraunhofer Absorption Line Spectroscopy with CIBER

Abstract Scattered sunlight from the interplanetary dust (IPD) cloud in our solar system presents a serious foreground challenge for spectrophotometric measurements of the extragalactic background light (EBL). In this work, we report on inferred measurements of the absolute intensity of the zodiacal light (ZL) using the novel technique of Fraunhofer line spectroscopy on the deepest 8542 Å line of the near-infrared Ca ii absorption triplet. The measurements are performed with the narrow band spectrometer (NBS) on board the Cosmic Infrared Background Experiment sounding rocket instrument. We use the NBS data to test the accuracy of two ZL models widely cited in the literature, the Kelsall and Wright models, which have been used in foreground removal analyses that produce high and low EBL results respectively. We find a mean reduced χ 2 = 3.5 for the Kelsall model and χ 2 = 2.0 for the Wright model. The best description of our data is provided by a simple modification to the Kelsall model, which includes a free ZL offset parameter. This adjusted model describes the data with a reduced χ 2 = 1.5 and yields an inferred offset amplitude of 46 ± 19 nW m−2 sr−1 extrapolated to 12500 Å. These measurements elude to the potential existence of a dust cloud component in the inner solar system whose intensity does not strongly modulate with the Earth’s motion around the Sun.

Measurement of the absolute gamma-ray emission intensities from the decay of 147Nd

The 2011 Decay Data Evaluation Project (DDEP) evaluation for 147Nd includes recommended absolute emission intensities for the two main gamma-rays at 91.105 (2) keV and 531.016 (22) keV of 0.284 (18) and 0.127 (9) respectively, i.e. with uncertainties of 6.3% and 7.1%. These large uncertainties stem from inconsistencies in the published data and are unfit for modern purposes, since the production of 147Nd is used as an important neutron flux dosimeter.The LNE-LNHB has undertaken new absolute gamma-ray emission intensity measurements. The results of these measurements will be presented, along with a full uncertainty budget, and their effect on the recommended data uncertainties will be discussed.

Measurements and modeling of CO 4th positive (A–X) radiation

We present absolute intensity measurements of CO 4th positive emission from a CO2/Ar plasma jet produced using an atmospheric pressure plasma torch facility. The centerline temperature of the plasma jet is approximately 6300 K. A VUV emission spectroscopy system was adapted to the plasma torch facility to measure spectrally resolved emission down to 140 nm. The emission from the plasma in the VUV, UV and near IR is consistent with thermochemical equilibrium. Carbon lines in the UV and VUV are found to be optically thick and their amplitude is therefore substantially affected by the line broadening parameters used for the calculation. For the CO 4th positive emission, these measurements test the performance of various models for the electronic transition moment function (ETMF). These ETMFs are used to calculate sets of Einstein coefficients that are used by SPECAIR to calculate the spectrally resolved emission of the plasma for comparison with experiments. We find that the EMTF of Kirby and Cooper and Spielfiedel accurately reproduce the measured emission from 150–215 nm.

Archaeointensity of nineteenth-century Scottish firebricks from a foundry in Melbourne, Australia: comparisons with field models and magnetic observatory data

AbstractAn archaeomagnetic intensity study was conducted on nineteenth-century firebricks manufactured in Scotland and used in an iron foundry in Melbourne, Australia, between 1842 and 1864 CE. Archaeointensity results obtained from bricks with a single component of magnetization gave values of 61.45 ± 0.89 and 61.92 ± 6.84 μT. These values are in agreement with historical absolute intensity measurements taken at the Melbourne geomagnetic observatory between 1858 and 1863 CE (61.17 ± 0.078 μT) and with the gufm1 model based on mariners’ data. A high-temperature vector component, presumably acquired at the time of manufacture in Scotland, was isolated in certain firebricks and an archaeointensity of 48.3 ± 8.39 μT was obtained, which is consistent with the gufm1 model for Scotland at this time (48.79 μT). The dual archaeointensity record of the firebricks supports their geographical provenance, highlighting the potential for archaeointensity data to be used in archaeological artefact-sourcing studies, whilst anomalously high intensities recorded in one of the bricks highlight potential contamination issues from non-Earth magnetic fields in archaeometallurgical contexts. The new Melbourne archaeointensity data are the most precisely dated archaeomagnetic data produced so far for Australia.

ANALYSIS OF GEOLOGICAL MATERIALS BY ICP-AES WITH CALIBRATION IN CONCENTRATION RATIO

A method of calibration in relative concentrations (concentration ratio) previously used only in analysis of non-ferrous and ferrous metals was first implemented when performing silicate analysis of geological materials using atomic emission spectrometry with inductively coupled plasma (AES-ICP). Prior to apply the Concentration Calibration Ratio to analysis of geological materials it is necessary to consider and address the following problems: some of the components are not determined by ICP-AES, matrix elements may be present in different oxidation states. Sample preparation of ores and geological materials was carried out in autoclaves heated at 180°C using HotBlock 200 system. A mixture HCl/HNO3/HF was used at the first step and then added with a 4% H3BO3 solution. The repeatability and intermediate precision of determination when using Concentration Ratio Calibration, calibration without internal standard and Calibration with In as internal standard are compared for determination of SiO2 (content 40 – 75%), Al2O3 (5 – 20%), CaO (0.25 – 15%), MgO (0.1 – 15%), Fe2O3 (0.5 – 15%), Na2O (0.5 – 10%), K2O (0.5 – 5%), P2O5 (0.01 – 0.3%), MnO (0.03 – 0.5%), and TiO2 (0.05 – 2%). The use of Concentration Ratio Calibration provides better metrological characteristics, repeatability and precision in analysis of geological materials compared to other calibration procedures due to elimination of the calibration error of balances and volumetric flasks from total error of analysis; measuring the large intensities of the base element; and better accuracy of measuring the intensity ratio compared to absolute intensity measurements.

Spectral instruments for x-ray and VUV plasma diagnostics

Spectral instruments for x-ray and VUV plasma diagnostics are described: focusing crystal spectrometer, several modifications of grazing incidence spectrometers and grazing incidence spectrometer-monochromator. Using spectroscopy methods these instruments could diagnose plasmas in a wide electron temperature range (Te ∼ 30 eV-1.5 keV) and provide absolute intensity measurements of various plasma sources.

Exploring Lanthanide Doping in UiO-66: A Combined Experimental and Computational Study of the Electronic Structure.

Lanthanide-based metal-organic frameworks show very limited stabilities, which impedes their use in applications exploiting their extraordinary electronic properties, such as luminescence and photocatalysis. This study demonstrates a fast and easy microwave procedure to dope UiO-66, an exceptionally stable and tunable Zr-based metal-organic framework. The generally applicable synthesis methodology is used to incorporate different transition metal and lanthanide ions. Selected experiments on these newly synthesized materials allow us to construct an energy scheme of lanthanide energy levels with respect to the UiO-66 host. The model is confirmed via absolute intensity measurements and provides an intuitive way to understand charge transfer mechanisms in these doped UiO-66 materials. Density functional theory calculations on a subset of materials moreover improve our understanding of the electronic changes in doped UiO-66 and corroborate our empirical model.

Absolute laser-intensity measurement and online monitor calibration using a calorimeter at a soft X-ray free-electron laser beamline in SACLA

This paper reports measurement of the absolute intensity of free-electron laser (FEL) and calibration of online intensity monitors for a brand-new FEL beamline BL1 at SPring-8 Angstrom Compact free-electron LAser (SACLA) in Japan. To measure the absolute intensity of FEL, we used a room-temperature calorimeter originally developed for FELs in the hard X-ray range. By using the calorimeter, we calibrated online intensity monitors of BL1, gas monitors (GMs), based on the photoionization of argon gas, in the photon energy range from 25 eV to 150 eV. A good correlation between signals obtained from the calorimeter and GMs was observed in the pulse energy range from 1 μJ to 100 μJ, where the upper limit is nearly equal to the maximum pulse energy at BL1. Moreover, the calibration result of the GMs, measured in terms of the spectral responsivity, demonstrates a characteristic photon-energy dependence owing to the occurrence of the Cooper minimum in the total ionization cross-section of argon gas. These results validate the feasibility of employing the room-temperature calorimeter in the measurement of absolute intensity of FELs over the specified photon energy range.

Antiferromagnetic ordering based on intermolecular London dispersion interactions in amphiphilic TEMPO ammonium salts.

Antiferromagnetic coupling in TEMPO-based radicals can be enhanced via self-assembly through London dispersion interactions in amphiphilic solids. The synthesis, magnetic characterization, and three crystal structures of the solid radical ion salts (R-DMAT-n)X with various counterions X and alkyl chain lengths n are reported. Magnetic susceptibility and absolute EPR signal intensity measurements show singlet-triplet transitions in a number of cases, which is discussed in relation to the crystal structures. Antiferromagnetic ordering effects are sensitive to both the length of the alkyl chain and the counter anion.

State-Specific Modeling of Vibrational Relaxation and Nitric Oxide Formation in Shock-Heated Air

A vibration-specific approach is employed to describe vibrational relaxation and reactive processes in shock-heated air. Models are implemented that include results from recent theoretical calculations for the relevant rate coefficients. Two sets of rate coefficients for the Zeldovich reactions of nitric oxide formation, derived from quasi-classical trajectory calculations, are compared. The relaxation kinetics, nitric oxide formation, and vibrational nonequilibrium behind the shock are discussed in detail. Results show that the nitric oxide formation kinetics is sensitive to the details of the adopted rate coefficients. The effect of the adopted kinetic descriptions (multitemperature, state-to-state) on the postshock plasma radiative signature is investigated. The predicted radiative contribution from the oxygen Schumann–Runge band is dominant in the spectral range 200–300 nm for shock speeds of . Comparison to shock-tube absolute intensity measurements has provided indications for improvement of nonequilibrium flow modeling. It is suggested that a kinetic treatment of the radiating electronic states may improve the agreement.

Light-emitting-diode Lambertian light sources as low-radiant-flux standards applicable to quantitative luminescence-intensity imaging.

Planar-type Lambertian light-emitting diodes (LEDs) with a circular aperture of several tens of μm to a few mm in diameter were developed for use as radiant-flux standard light sources, which have been in strong demand for applications such as quantitative or absolute intensity measurements of weak luminescence from solid-state materials and devices. Via pulse-width modulation, time-averaged emission intensity of the LED devices was controlled linearly to cover a wide dynamic range of about nine orders of magnitude, from 10 μW down to 10 fW. The developed planar LED devices were applied as the radiant-flux standards to quantitative measurements and analyses of photoluminescence (PL) intensity and PL quantum efficiency of a GaAs quantum-well sample. The results demonstrated the utility and applicability of the LED standards in quantitative luminescence-intensity measurements in Lambertian-type low radiant-flux level sources.

High-order multiphoton Thomson scattering

Electron–photon scattering, or Thomson scattering, is one of the most fundamental mechanisms in electrodynamics, underlying laboratory and astrophysical sources of high-energy X-rays. After a century of studies, it is only recently that sufficiently high electromagnetic field strengths have been available to experimentally study the nonlinear regime of Thomson scattering in the laboratory. Making use of a high-power laser and a laser-driven electron accelerator, we made the first measurements of high-order multiphoton scattering, in which more than 500 near-infrared laser photons were scattered by a single electron into a single X-ray photon. Both the electron motion and the scattered photons were found to depend nonlinearly on field strength. The observed angular distribution of scattered X-rays permits independent measurement of absolute intensity, in situ, during interactions of ultra-intense laser light with free electrons. Furthermore, the experiment's potential to generate attosecond-duration hard X-ray pulses can enable the study of ultrafast nuclear dynamics. More than 500 near-infrared laser photons are scattered by a single electron into a single X-ray photon. This is the first experimental evidence of high-order multiphoton Thomson scattering and validates the decades-old theoretical predictions.

Objective Quantification of Anterior Chamber Inflammation: Measuring Cells and Flare by Anterior Segment Optical Coherence Tomography

To assess the ability of swept-source (SS) optical coherence tomography (OCT) of the anterior segment (AS) to measure anterior chamber (AC) inflammation (both flare and cells) objectively. To compare OCT-derived inflammatory indices with standard techniques. Prospective evaluation of a diagnostic test. Patients diagnosed with anterior uveitis (active or inactive) and controls. Participants underwent an AC inflammation evaluation including: clinical cell and flare grading and laser flare photometry (LFP). Uveitis patients were divided into active or inactive uveitis status according to clinical grading. Anterior segment SS-OCT scans were obtained for each participant. Tomographic images were analyzed to count the AC cells, and to calculate to absolute measurements of aqueous signal intensity. The absolute values were compared with the signal measured by the scan outside the eye, generating an optical density ratio (aqueous-to-air relative intensity [ARI] index). Correlations between OCT-derived AC inflammatory indexes and LFP, clinical grading, participant category (active or inactive uveitis, control), age, gender, and central corneal thickness (CCT) were assessed. Correlation between OCT-derived AC inflammatory indexes (ARI index and AC cells on OCT) and standard clinical techniques (LFP, clinical cell grading). Two hundred thirty-seven eyes (70 active uveitis, 97 inactive uveitis, and 70 controls) were included. Anterior chamber cells count on OCT did not differ between inactive uveitis and controls, but was significantly higher in active uveitis compared to the other categories (both P < 0.0001). All groups had different LFP (all P < 0.0001). Active uveitis had significantly higher ARI index compared with inactive uveitis and controls (both P < 0.0001). Interobserver agreement (intraclass correlation coefficient) for ARI index was 0.78. The ARI index correlated positively with age (P= 0.043) and negatively with CCT (P= 0.006). The ARI index correlated with LFP in the active uveitis group (P < 0.0001), but not in the others. Anterior chamber cells on OCT increased among all cell clinical grades (P < 0.0001). The ARI index increased among all flare clinical grades (P < 0.005). Anterior segment SS-OCT could be used for a comprehensive assessment of AC inflammation, providing objective measurements of inflammatory cells and aqueous flare.

100 GHz Room-Temperature Laboratory Emission Spectrometer

AbstractWe present first results of a new heterodyne spectrometer dedicated to high-resolution spectroscopy of molecules of astrophysical importance. The spectrometer, based on a room-temperature heterodyne receiver, is sensitive to frequencies between 75 and 110 GHz with an instantaneous bandwidth of currently 2.5 GHz in a single sideband. The system performance, in particular the sensitivity and stability, is evaluated. Proof of concept of this spectrometer is demonstrated by recording the emission spectrum of methyl cyanide, CH3CN. Compared to state-of-the-art radio telescope receivers the instrument is less sensitive by about one order of magnitude. Nevertheless, the capability for absolute intensity measurements can be exploited in various experiments, in particular for the interpretation of the ever richer spectra in the ALMA era. The ease of operation at room-temperature allows for long time integration, the fast response time for integration in chirped pulse instruments or for recording time dependent signals. Future prospects as well as limitations of the receiver for the spectroscopy of complex organic molecules (COMs) are discussed.