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ncs-Si–SiOx:Sm structures formed by high-temperature air annealing of the SiOx films doped with samarium during thermal co-evaporation in vacuum of silicon monoxide and metallic Sm was studied. By measuring the spectra of photoluminescence (PL), it has been shown that doping of SiOx films with Sm stimulates their decomposition into Si and SiO2, and also reduces the transition temperature of silicon nanoparticle from the amorphous state to the crystalline one. With an increase in the impurity content up to 2 wt.%, along with the ncs-Si luminescence, the PL spectrum exhibits emission bands of Sm3+ and Sm2+ ions, which do not appear at a lower Sm concentration. The presence of silicon nanocrystals in SiOx films doped with Sm and annealed at 970 °C in air has been confirmed using Raman scattering spectra. A possible mechanism for interaction of samarium ions with the SiOx matrix and ncs-Si has been discussed. [ABSTRACT FROM AUTHOR]

The luminescent spectra of the RE 2 O 3 -doped P 2 O 5 -CdO-ZnO glasses (RE = Er, and Tb) were investigated to separate the effects of two studied rare-earth elements and the annealing regime on the emission performance of the prepared glasses. The glasses undergo a series of collective measurements including UV-visible absorption, luminescence, thermal expansion, XRD, TEM, and FTIR. The optical UV-visible spectra of the two doped glasses reveal a UV band due to undoped glass beside and extra extended 11 peaks with the Er 3+ ions with high distinct features while the Tb 3+ ions samples exhibit peaks within the visible region. These peaks are correlated with transitions from the ground state in each case to specific energy transitions. The overall optical data indicate that the two rare earth ions are present in a stable trivalent state. Under UV excitation, both Er 3+ and Tb 3+ emit a characteristic green light corresponding to 4 S 3/2  →  4 I 15/2 and 5 D 4  →  7 F 5 transitions, respectively. The performance of the green light was identified to be enhanced by increasing the concentration of rare earth and the effect of annealing temperature. Moreover, the intensity of the infrared emission of Er 3+ at 1532 nm corresponds to the ( 4 I 13/2  →  4 I 15/2 ) transition which is assumed to be developed with the effect of heating. The resultant IR spectra show distinct vibrational peaks due to phosphate groups that undergo only minor modifications when doped with rare earth elements or over-annealed., (© 2024. The Author(s).)

Observations of H i Lyman α, the brightest UV emission line of late-type stars, are critical for understanding stellar chromospheres and transition regions, modeling photochemistry in exoplanet atmospheres, and measuring the abundances of neutral hydrogen and deuterium in the interstellar medium. Yet Lyα observations are notoriously challenging owing to severe attenuation from interstellar gas, hindering our understanding of this important emission line's basic morphology. We present high-resolution far- and near-UV spectroscopy of five G, K, and M dwarfs with radial velocities large enough to Doppler-shift the stellar Lyα emission line away from much of the interstellar attenuation, allowing the line core to be directly observed. We detect self-reversal in the Lyα emission-line core for all targets, and we show that the self-reversal depth decreases with increasing surface gravity. Mg ii self-reversed emission-line profiles provide some useful information to constrain the Lyα line core, but the differences are significant enough that Mg ii cannot be used directly as an intrinsic Lyα template during reconstructions. We show that reconstructions that neglect self-reversal could overestimate intrinsic Lyα fluxes by as much as 60%–100% for G and K dwarfs and 40%–170% for M dwarfs. The five stars of our sample have low magnetic activity and subsolar metallicity; a larger sample size is needed to determine how sensitive these results are to these factors. [ABSTRACT FROM AUTHOR]

Laser-induced fluorescence (LIF) is a widely used technique for both laboratory-based and ambient atmospheric chemistry measurements. However, LIF instruments require calibrations in order to translate instrument response into concentrations of chemical species. Calibration of LIF instruments measuring OH and HO2 (HOx) typically involves the photolysis of water vapor by 184.9 nm light, thereby producing quantitative amounts of OH and HO2. For ground-based HOx instruments, this method of calibration is done at one pressure (typically ambient pressure) at the instrument inlet. However, airborne HOx instruments can experience varying cell pressures, internal residence times, temperatures, and humidity during flight. Therefore, replication of such variances when calibrating in the lab is essential to acquire the appropriate sensitivities. This requirement resulted in the development of the APACHE (All Pressure Altitude-based Calibrator for HOx Experimentation) chamber to characterize the sensitivity of the airborne LIF-FAGE (fluorescence assay by gas expansion) HOx instrument, HORUS, which took part in an intensive airborne campaign, OMO-Asia 2015. It utilizes photolysis of water vapor but has the additional ability to alter the pressure at the nozzle of the HORUS instrument. With APACHE, the HORUS instrument sensitivity towards OH (26.1–7.8 cts s -1 pptv -1 mW -1 , ±22.6 % 1σ ; cts stands for counts by the detector) and HO2 (21.2–8.1 cts s -1 pptv -1 mW -1 , ±22.1 % 1σ) was characterized to the external pressure range at the instrument nozzle of 227–900 mbar. Measurements supported by a computational fluid dynamics model, COMSOL Multiphysics, revealed that, for all pressures explored in this study, APACHE is capable of initializing a homogenous flow and maintaining near-uniform flow speeds across the internal cross section of the chamber. This reduces the uncertainty regarding average exposure times across the mercury (Hg) UV ring lamp. Two different actinometrical approaches characterized the APACHE UV ring lamp flux as 6.37×1014(±1.3×1014) photons cm -2 s -1. One approach used the HORUS instrument as a transfer standard in conjunction with a calibrated on-ground calibration system traceable to NIST standards, which characterized the UV ring lamp flux to be 6.9(±1.1)×1014 photons cm -2 s -1. The second approach involved measuring ozone production by the UV ring lamp using an ANSYCO O3 41 M ozone monitor, which characterized the UV ring lamp flux to be 6.11(±0.8)×1014 photons cm -2 s -1. Data presented in this study are the first direct calibrations of an airborne HOx instrument, performed in a controlled environment in the lab using APACHE. [ABSTRACT FROM AUTHOR]

We have measured photoluminescence spectra of an aqueous uranyl chloride solution under excitation by various light sources: semiconductor light-emitting diodes and cw laser. The excitation wavelength lay within a resonance absorption band of uranyl chloride, which ensured photoluminescence detection at exposure times of 10-3 s using an extremely small volume of the substance (10-9 cm3). The photoluminescence spectra were measured using a small minispectrometer, which allowed us to analyze the spectra in the range 200-1000 nm. [ABSTRACT FROM AUTHOR]

The X-ray-luminescence spectra of glassy and polycrystalline lithium tetraborate Li2B4O7 activated by europium oxide Eu2O3 are studied in the spectral range of 200 to 800 nm. The luminescence observed in the wavelength region of 570 to 720 nm is caused by intraconfiguration f-f electron transitions between the levels of the first excited multiplet 5D and the main multiplet 7F of the Eu3+ ion. [ABSTRACT FROM AUTHOR]

Rich sampling and modern research techniques, including SEM, revealed that rarely collected epilachnine species Epiverta chelonia is a complex of four closely related species: E. chelonia (Mader, 1933), E. albopilosa, E. angusta, and E. supinata spp. nov. All Epiverta species are described and illustrated, a key to the species and a distribution map are provided. Lectotype of Solanophila chelonia Mader, 1933 is designated and its type locality delimited to Yunnan Province, Deqin County (China). [ABSTRACT FROM AUTHOR]

Reflectance spectroscopy in the visible to short-wave infrared regions (500 to 2500 nm) was carried out using natural samples of the rare earth element (REE) phosphate minerals monazite, xenotime, and britholite. Samples were characterized by scanning electron microscopy and electron microprobe analysis. Absorption band positions were recorded with their probable origins, and spectral variability among the samples is discussed. Spectral features of these minerals are driven primarily by 4f-4f intraconfigurational electronic transitions of trivalent lanthanides. The distinct REE distributions of monazite, xenotime, and britholite drive their bulk spectral patterns, which in turn are sufficiently distinct to enable spectral classification. Spectral variability of some specific REE-related absorptions are interpreted to be driven by differences of the coordination polyhedra for the lanthanide cations between the crystal structures. Spectra of these minerals were also compared against carbonatitehosted REE bearing fluorapatite. The work presented here strengthens the growing foundation for the interpretation of reflectance spectra of these REE phosphate minerals and enables exploitation of the observed features by the remote sensing community for detection, identification, and quantification of REE phosphate minerals. This is especially relevant for hyperspectral imaging spectroscopy with high spatial resolution, where the spectral response of a pixel becomes increasingly dominated by mineralogy. [ABSTRACT FROM AUTHOR]

Ladybird beetle is important group of beetles because they are important universal predatory and occupies important place in biological control. However, the ladybird beetle fauna of Pakistan is not extensively explored area wise. In this connection, the present study was conducted to explore the Ladybird beetle fauna of district Buner, Khyber Pakhtunkhwa, Pakistan. The study area was divided into twelve different localities namely village (Pirbaba, Kingergali, Daggar, Gokand, Barkalay, Budal, Shaheede sar, Nawagai, Nagrai, Chinglai, Totalai and Malka). Collection surveys were conducted in these areas at fifteen days interval in the active season during 2013-14. The identification of the collected specimens during the study revealed that there are thirteen species of Ladybird beetle under eleven genera and three subfamilies (Subfamily Chilocorinae, Subfamily Coccinellini and Subfamily Epilachnini) were collected. These species are Brumoidus suturalis, Coccinella septempunctata, Coccinella transversalis, Menochilus sexmaculatus, Propylea dissecta, Coelophora bissellata, Oenopia sauzeti, Aiolocaria hexaspilota, Psyllobora bisoctonotata, Harmonia dimidiata, Henosepilachna vigintioctopunctata, Henosepilachna septima and Afidentula manderstjernae. The numerical data of these species reveals that C. septempunctata, H. dimidiata, C. sexmaculatus and H. vigintioctopunctata are highly abundant and were collected from all localities, while the rest of the species are moderately abundant except A. hexaspilota which is only collected from single locality pirbaba. [ABSTRACT FROM AUTHOR]

A new type of novel orange-red emitting Eu-doped ZnO/TiO nanocomposite phosphors have been synthesized by simple low temperature co-precipitation route. Structure and morphology of the prepared sample have been investigated using X-ray diffraction and field emission scanning electron microscopy (FESEM) techniques. XRD pattern confirmed the presence of both phases of ZnO and TiO simultaneously. The luminescence properties, such as photoluminescence (PL) excitation and emission spectra, Judd-Ofelt parameters, CIE colour coordinates and the dependence of luminescence intensity on the doping level were investigated. The luminescence spectrum characteristics of Eu ions have a strong dependence on Eu doping levels as well as ZnO/TiO ratio variations. The photoluminescence results indicate that these phosphors could be efficiently excited by near-ultraviolet radiation, which causes emissions in orange-red regions. [ABSTRACT FROM AUTHOR]

The simplest components (atoms, diatomic molecules, and simple free radicals) of an inductively coupled rf plasma in a hexamethyldisilazane-argon mixture have been identified by optical emission spectroscopy. We have studied the influence of process conditions (plasma power and hexamethyldisilazane concentration in the mixture) on the intensity of lines and bands corresponding to these components and the corresponding changes in the composition and physicochemical properties of SiCNH films grown in this plasma. [ABSTRACT FROM AUTHOR]

Metal-organic frameworks assembled from Ln(III), Li(I) and rigid dicarboxylate ligand, formulated as [LiLn(BDC)2(H2O)·2(H2O)] (MS1-6,7a) and [LiTb(BDC)2] (MS7b) (Ln = Tb, Dy, Ho, Er, Yb, Y0.96Eu0.04, Y0.93Tb0.07, and H2BDC = terephthalic acid), were obtained under hydrothermal conditions. The isostructural MS1-6 crystallize in monoclinic P21/c space group. While, in the case of Tb3+ a mixture of at least two phases was obtained, the former one (MS7a) and a new monoclinic C2/c phase (MS7b). All compounds have been studied by single-crystal and powder X-ray diffraction, thermal analyses (TGA), vibrational spectroscopy (FTIR), and scanning electron microscopy (SEM-EDX). The structures of MS1-6 and MS7a are built up of inorganic-organic hybrid chains. These chains constructed from unusual four-membered rings, are formed by edge- and vertex-shared {LnO8} and {LiO4} polyhedra through oxygen atoms O3 (vertex) and O6-O7 (edge). Each chain is cross-linked to six neighboring chains through six terephthalate bridges. While, the structure of MS7b is constructed from double inorganic chains, and each chain is, in turn, related symmetrically to the adjacent one through the c glide plane. These chains are formed by infinitely alternating {LiO4} and {TbO8} polyhedra through (O2-O3) edges to create Tb-O-Li connectivity along the c-axis. Both MS1-6,7a and MS7b structures possess a 3D framework with 1D trigonal channels running along the a and c axes, containing water molecules and anhydrous, respectively. Topological studies revealed that MS1-6 and MS7a have a new 2-nodal 3,10-c net, while MS7b generates a 3D net with unusual β-Sn topology. The photoluminescence properties Eu- and Tb-doped compounds (MS5-6) are also investigated, exhibiting strong red and green light emissions, respectively, which are attributed to the efficient energy transfer process from the BDC ligand to Eu3+ and Tb3+. [ABSTRACT FROM AUTHOR]

Based on the recent revised generic classification of the tribe Epilachnini (Szawaryn et al. 2015), all 27 genera are re-described, diagnosed, illustrated, and included in an identification key. The following nomenclatural changes are made: Epilachna (Hypsa) Mulsant 1850, Epilachna (Cleta) Mulsant 1850, Solanophila Weise 1898, Epilachna (Aparodentata) Wang and Cao 1993, and Epilachna (Uniparodentata) Wang and Cao 1993 are removed from synonymy of Epilachna Chervolat 1837. The subgenus Cleta of Epilachna is raised to the genus level, as Cleta Mulsant 1850 stat. nov.; the subgenus Uniparodentata of Epilachna is raised to the genus level, as Uniparodentata Wang and Cao 1993 stat. nov. Chazeauiana Tomaszewska and Szawaryn 2015 (type species, Epilachna sahlbergi Mulsant 1850), and Epilachna (Hypsa) Mulsant 1850 (type species, Epilachna nigrolimbata Thomson 1875) are synonymized here under the name Cleta Mulsant 1850 (type species, Epilachna eckloni Mulsant 1850)—new synonyms; Fuerschia Tomaszewska and Szawaryn 2015 (type species, Coccinella canina Fabricius 1781) is synonymized with Solanophila Weise 1898 (type species, Epilachna gibbosa Crotch 1874)—new synonym; Ryszardia Tomaszewska and Szawaryn 2015 (type species, Epilachna decipiens Crotch 1874) and Epilachna (Aparodentata) Wang and Cao, 1993 (type species, Epilachna yongshanensis Cao and Xiao 1984) are synonymized under the name Uniparodentata Wang and Cao 1993 (type species, Epilachna paramagna Pang and Mao 1979)—new synonyms. Henosepilachna (Elateria) Fürsch 1964 (type species: Coccinella elaterii Rossi 1794) is removed from synomyms of Henosepilachna Li 1961 [type species, Coccinella sparsa Herbst 1786 (=Coccinella vigintioctopunctata Fabricius 1775)] and is synonymized here with Chnootriba Chevrolat 1837 (type species: Coccinella similis Thunberg 1781)—new synonym. Coccinella flavofasciata Laporte 1840, Epilachna aequatorialis Gordon 1975, E. bizonata Crotch 1874, E. convergens Crotch 1874, E. cruciata Mulsant 1850, E. dubia Crotch 1874, E. monovittata Gordon 1975, E. orthostriata Gordon 1975, E. paracuta Gordon 1975, E. patricia Mulsant 1850, E. satipensis Gordon 1975, and E. univittata Crotch 1874 are transferred to Toxotoma Weise 1900 (comb. nov.); Afissa chapini Dieke 1947, A. complicata Dieke 1947, A. convexa Dieke 1947, A. magna Dieke 1947, A. militaris Dieke 1947, A. quadricollis Dieke 1947, A. subacuta Dieke 1947, A. szechuana Dieke 1947, Epilachna boymi Jadwiszczak and Węgrzynowicz 2003, E. crepida Pang and Ślipiński 2012, E. decipiens Crotch 1874, E. dorotae Bielawski 1979, E. hamulifera Pang and Ślipiński 2012, E. malleforma Peng, Pang and Ren 2002, E. siphodenticulata Hoàng 1983, E. angusta Li 1961, E. bifibra Li 1961, E. chingjing Yu and Wang 1999, E. circumdata Hoàng 1978, E. circummaculata Pang and Mao 1977, E. clematicola Cao and Xiao 1984, E. exornata Bielawski 1965, E. folifera Pang and Mao 1979, E. fugongensis Cao and Xiao 1984, E. glochisifoliata Pang and Mao 1979, E. gressiti Li 1961, E. lata Li 1961, E. madanensis Zeng 2002, E. media Li 1961, E. mobliteratiae Li 1961, E. yongshanensis Cao and Xiao 1984, Solanophila acuta Weise 1900, and S. saginata Weise 1902 are transferred to Uniparodentata Wang and Cao 1993 (comb. nov.); Coccinella canina Fabricius 1781, Epilachna dregei Mulsant 1850, E. infirma Mulsant 1850, E. murrayi Crotch 1874 and E. paykullii Mulsant 1850 are transferred to Solanophila Weise 1898 (comb. nov.); Afissula antennata Bielawski 1967, A. rana Kapur 1958, A. uniformis Pang and Mao 1979, Epilachna ampliata Pang and Mao 1979, E. flavimarginalis Hoàng 1978, E. max Pang and Ślipiński 2012, E. parvula Crotch, E. plicata Weise 1889, and E. sanscrita Crotch 1874 are transferred to Afissa Dieke 1947 (comb. nov.); Epilachna papuensis Crotch 1874 and Subafissa brittoni Bielawski 1963 are transferred to Henosepilachna Li 1961 (comb. nov.); Epilachna admirabilis Crotch 1874, E. alternans Mulsant 1850, E. glochinosa Pang and Mao 1979, E. hopeiana Miyatake 1985, E. insignis Gorham 1892, E. macularis Mulsant 1850, E. parainsignis Pang and Mao 1979, and Solanophila maxima Weise 1898 are transferred to Diekeana Tomaszewska and Szawaryn 2015 (comb. nov.); Epilachna fulvohirta Weise 1895, E. nigrolimbata Thomson 1875, Henosepilachna griveaudi Chazeau 1975, H. vadoni Chazeau 1976, Solanophila consignata Weise 1909, S. coquereli Sicard 1907, and S. gyldenstolpei Weise 1924 are transferred to Cleta Mulsant 1850 (comb. nov.); Afidenta janczyki Fürsch 1986, Epilachna capicola Mulsant 1850, E. godarti Mulsant 1850, E. scitula Weise 1898, Henospeilachna acervata Chazeau 1975, and Solanophila blaesa Weise 1905 are transferred to Afidentula Kapur 1958 (com. nov.); Coccinella elaterii Rossi 1794, C. hirta Thunberg 1781, C. pavonia Olivier 1808, Epilachna annulata Kolbe 1897, E. biplagiata Kolbe 1897, E. cinerascens Weise 1907, E. connectens Weise 1912, E. erichi Weise, 1897, E. occellata Bertoloni, 1849, E. pauli Weise, 1897, E. tetracycla Gerstaecker, 1871, E. umbratilis Weise 1909, E. vulgaris Weise 1901, Henosepilachna bigemmata Fürsch 1991, Solanophila guttifera Weise 1899, S. hova Weise 1905, and S. kaffaeensis Weise 1906 are transferred to Chnootriba Chevrolat 1837 (com. nov.); Coccinella guttatopustulata Fabricius 1775, Epilachna aruensis Crotch 1874, E. biroi Weise 1902, E. buqueti Montrouzier 1861, E. fulvimana Weise 1903, E. immaculata Bielawski 1963, E. karapensis Bielawski 1963, E. orrori Bielawski 1963, E. samuelsoni Jadwiszczak 1991, and E. slipinskii Jadwiszczak 1987 are transferred to Papuaepilachna Tomaszewska and Szawaryn, 2013 (comb. nov.). The history of classification, the known aspects of the biology and distributional data of the tribe are summarized. [ABSTRACT FROM AUTHOR]

Scintillator materials are widely used for a variety of applications such as high energy physics, astrophysics and medical imaging. Since the ideal scintillator does not exist, the search for scintillators with suitable properties for each application is of great interest. Here, Pr 3+ -doped KGd(PO 3 ) 4 bulk single crystals with monoclinic structure (space group: P2 1 ) are grown from high temperature solutions and their structural, thermal and optical properties are studied as possible candidates for scintillation material. The change in the unit cell parameters as a function of the Pr 3+ level of doping and temperature is studied. Differential thermal analysis reveals that KGd 0.942 Pr 0.058 (PO 3 ) 4 is stable until 1140 K. The 5d 3 , 5d 2 and 5d 1 levels of Pr 3+ with respect to the 3 H 4 ground state are centred at 166, 196 and 218 nm, respectively, in this host. The luminescence of KGd 0.990 Pr 0.010 (PO 3 ) 4 , by exciting these 5d levels, shows intense emissions centred at 256 and 265 nm from the 5d 1 to 3 F 3,4 and 1 G 4 levels of Pr 3+ with a short decay time of 6 ns. The 6 P 3/2,5/2,7/2  →  8 S 7/2 transitions of Gd 3+ appear after exciting the 5d levels of Pr 3+ and the 4 f levels of Gd 3+ , showing an energy transfer between Pr 3+ and Gd 3+ .

Combustion process was studied from the injection until the late combustion phase in an high swirl optically accessible combustion bowl connected to a single cylinder two-stroke high pressure common rail compression ignition engine. Commercial diesel and blends of diesel and n-butanol (20%: BU20 and 40%: BU40) were used for the experiments. A pilot plus main injection strategy was investigated fixing the injection pressure and fuel mass injected per stroke. Two main injection timings and different pilot- main dwell times were explored achieving for any strategy a mixing controlled combustion. Advancing the main injection start, an increase in net engine working cycle (>40%) together with a strong smoke number decrease (>80%) and NOx concentration increase (≃50%) were measured for all pilot injection timings. Compared to diesel fuel, butanol induced a decrease in soot emission and an increase in net engine working area when butanol ratio increased in the blend. A noticeable increase in NOx was detected at the exhaust for BU40 with a slight effect of the dwell-time. Spectroscopic investigations confirmed the delayed auto-ignition (∼ 60 μs) of the pilot injection for BU40 compared to diesel. The spectral features for the different fuels were comparable at the start of combustion process, but they evolved in different ways. Broadband signal caused by soot emission, was lower for BU40 than diesel. Different balance of the bands at 309 and 282 nm, due to different hydrooxide transitions, were detected between the twofuels. The ratio of these intensities was used tofollow flame temperature evolution. [ABSTRACT FROM AUTHOR]

Although imaging techniques using soft X-rays (SXs) are being developed as the available photon flux increases because of the continuing development of synchrotron light sources, it will be necessary to downsize the pixel size of the SX camera to produce finer SX images. Application of the stimulated emission depletion (STED) method to a scintillator plate followed by use of this plate as a sensor is one promising method to reduce the pixel size of SX cameras. A STED phenomenon occurred in the luminescence of a Ce-doped Lu 2 SiO 5 crystal (Ce:LSO) excited using ultraviolet (UV) light when the scintillator was irradiated with azimuthally polarized laser light in the photon energy range from 1.97 eV (630 nm) to 2.58 eV (480 nm). When the excitation light source changed to synchrotron radiation (SR) light with photon energy of 800 eV, the same STED phenomenon occurred. The spot size of the luminescence was reduced by the STED phenomenon and this spot size decreased as the STED laser's photon energy increased. The energy dependence of the Ce:LSO luminescence levels can be used to explain the change in the spot size at the luminescence point.

In this study, an in situ application for identifying neodymium (Nd) enriched surface materials that uses multitemporal hyperspectral images is presented (HySpex sensor). Because of the narrow shape and shallow absorption depth of the neodymium absorption feature, a method was developed for enhancing and extracting the necessary information for neodymium from image spectra, even under illumination conditions that are not optimal. For this purpose, the two following approaches were developed: (1) reducing noise and analyzing changing illumination conditions by averaging multitemporal image scenes and (2) enhancing the depth of the desired absorption band by deconvolving every image spectrum with a Gaussian curve while the rest of the spectrum remains unchanged (Richardson-Lucy deconvolution). To evaluate these findings, nine field samples from the Fen complex in Norway were analyzed using handheld X-ray fluorescence devices and by conducting detailed laboratory-based geochemical rare earth element determinations. The result is a qualitative outcrop map that highlights zones that are enriched in neodymium. To reduce the influences of non-optimal illumination, particularly at the studied site, a minimum of seven single acquisitions is required. Sharpening the neodymium absorption band allows for robust mapping, even at the outer zones of enrichment. From the geochemical investigations, we found that iron oxides decrease the applicability of the method. However, iron-related absorption bands can be used as secondary indicators for sulfidic ore zones that are mainly enriched with rare earth elements. In summary, we found that hyperspectral spectroscopy is a noninvasive, fast and cost-saving method for determining neodymium at outcrop surfaces. [ABSTRACT FROM AUTHOR]

A series of natural zircon samples (with U concentrations of 140-2600 ppm and ranging from well crystalline to severely radiation damaged) were investigated by means of REE3+ photoluminescence spectroscopy. We found systematic changes in REE3+ emissions depending on the accumulated radiation damage expressed by the effective time-integrated a-dose of zircon samples. Structural reconstitution as caused by dry annealing resulted in intensity gains and decreases of half-widths of REE3+ emissions. The band half-widths of distinct luminescence Stark's levels of the 4F9/2 → 6H13/2 transition of Dy3+ (~17 250 cm-1; ~580 nm wavelength) and the 4F3/2 → 4I9/2 transition of Nd3+ (~11 300 cm-1; ~885 nm wavelength) were found to correlate sensitively with the degree of radiation damage accumulated. These REE3+ emissions are proposed as potential measure of the irradiation-induced structural disorder of zircon. The two emissions are considered particularly suitable because (1) they are commonly detected in PL spectra of natural zircon, and (2) they are hardly biased by other emissions or Stark's levels. Preliminary calibration curves that relate band-width increases to the a dose were established using a suite of well-characterized Sri Lankan zircon. Band broadening upon increasing corpuscular self-irradiation is assigned to increasing structural destruction, i.e., the increasing perturbation of REE3+ cationic lattice sites. Possible advantages of REE3+ luminescence spectroscopy, complementary to Raman spectroscopy, as method to quantify structural radiation damage are discussed. [ABSTRACT FROM AUTHOR]

An understanding of the mineralogy and petrogenesis of rare earth element deposits has significant implications for their economic viability. Lanthanide-bearing compounds are known to produce sharp absorption features in the visible to short-wave infrared region (VIS-SWIR), however, a significant knowledge gap exists between the fields of hyperspectral reflectance spectroscopy and rare earth element mineralogy. Reflectance spectra were collected from four bastnäsite samples, two parisite samples, and one synchysite sample from the visible into the short-wave infrared. These REE fluorocarbonate mineral samples were characterized via scanning electron microscopy and electron probe microanalysis. Sharp absorptions of REE-bearing minerals are mostly the result of 4f-4f intraconfigurational electron transitions and for the light REE-enriched fluorocarbonates, the bulk of the features can be ascribed to Nd3+, Pr3+, Sm3+, and Eu3+. The lanthanide-related spectral responses of the REE fluorocarbonates are consistent across the group, supporting the notion that the REE cation site is very similar in each of these minerals. Carbonate-related spectral responses differed between these minerals, supporting the notion that the crystallographic sites for the carbonate radical differ between bastnäsite, synchysite, and parisite. Exploitable spectral differences include a distinct absorption band at 2243 nm that separates bastnäsite from synchysite and parisite. Similarly, for bastnäsite a dominantly Pr3+-related absorption band located is at 1968 nm, while in synchysite and parisite it occurs at 1961 nm. [ABSTRACT FROM AUTHOR]

Thermally stimulated luminescence (TSL) investigations of SrBPO:Eu and SrBPO:Eu phosphors were carried out in the temperature range of 300-650 K. In order to characterize the phosphors, X-ray diffraction and photoluminescence (PL) techniques were used. The emission spectrum of air heated SrBPO:Eu phosphor exhibited emission bands at 590, 614, 651 and 702 nm under 248 nm excitation, assigned to transitions of Eu ion. In phosphor prepared in reducing (Ar + 8% H) atmosphere, a broad emission band due to Eu ranging from 350 to 400 nm was observed with 340 nm excitation. EPR studies have confirmed the presence of Eu ions in the samples prepared in reducing atmosphere. TSL glow curve of SrBPO:Eu had shown intense peaks around 397, 510, 547 K and a weak peak around 440 K whereas in case of SrBPO:Eu system, glow peaks at 414, 478 and weak peak at 516 nm were observed. The shift in TSL glow pattern can be attributed to stabilization of different oxidation states of the dopant ion in the host lattice. Apart from this, TSL trap parameters such as trap depth and frequency factor were determined. Spectral characteristics of TSL emission have shown that Eu/Eu ion acts as the luminescent centre in the respective phosphors. [ABSTRACT FROM AUTHOR]

Rare earth ions embedded in host crystals are of great interest for many applications. Due to the crystal field of the host material, the energy levels of the rare earth ions split into several Stark levels. The resulting broadening of the spectral line shapes of transitions between those levels determines the upconversion phenomena, especially under broad-spectrum illumination, which are relevant for photovoltaics for instance. In this paper, we present a method to determine the spectral line shape of energy level transitions of rare earth ions from the absorption spectrum of the investigated material. A parameter model is used to describe the structure of the individual energy levels based on a representation of the Stark splitting. The parameters of the model are then determined with an evolutionary optimization algorithm. The described method is applied to the model system of β-NaEr0.2Y0.8F4. The results indicate that for illumination with a wavelength around 1523 nm, simple upconversion processes such as two-step absorption or direct energy transfer are less efficient than commonly assumed. Hence a sequence of efficient processes is suggested as an explanation for the high upconversion quantum yield of β-NaEr0.2Y0.8F4, which has not yet been reported in the literature. [ABSTRACT FROM AUTHOR]

The present study experimentally demonstrated that solid H2O is formed through the surface reaction OH + H2 at 10 K. This is the first experimental evidence of solid H2O formation using hydrogen in its molecular form at temperatures as low as 10 K. We further found that H2O formation through the reaction OH + H2 is about one order of magnitude more effective than HDO formation through the reaction OH + D2. This significant isotope effect results from differences in the effective mass of each reaction, indicating that the reactions proceed through quantum tunneling. [ABSTRACT FROM AUTHOR]

The photoluminescence (PL) and PL excitation (PLE) spectra of Si6-zAlzOzN8-z ([beta]-sialon):Eu2+ phosphors with small z values (z = 0.025-0.24) were studied at room temperature and 6 K. The PL and PLE spectra exhibit fine structure with the PL lines being as sharp as 45-55 nm even at room temperature; this fine structure was enhanced by decreasing the z value. These results can be used for expanding the color gamut of liquid crystal displays, particularly in the blue-green region. From low-temperature measurements, the fine PLE structure was ascribed to discrete energy levels of 7FJ states. The 4f65d excited states of Eu2+ are considered to be localized near the 4f orbital. This is because the bonding of Eu2+ with surrounding atoms is ionic rather than covalent. Lattice phonon absorptions were also observed in the PLE spectrum, revealing that the optically active Eu2+ ions are located in the [beta]-sialon crystal. The PL spectrum of the sample with the smallest z value (0.025) consists of a sharp zero-phonon line and lattice phonon replicas, which results in a sharp and asymmetric spectral shape. [ABSTRACT FROM AUTHOR]

In this paper, we report the synthesis of Ce and Dy activated alkali lanthanide tungstates, ALa(WO)(where A = Na and Li), prepared by solid state reaction method. The prepared phosphors were characterized by X-ray diffraction and photoluminescence techniques. The NaLa(WO):Dy and LiLa(WO):Dy phosphors show two emission peaks at around 574 and 486 nm (λ = 354 nm). NaLa(WO):Ce and LiLa(WO):Ce show two emission peaks at around 378 and 425 nm (λ = 350 nm). Excitation wavelengths of Ce and Dy activated alkali lanthanide tungstates are in near UV region i.e. Hg free excitation. These characterizations of phosphors are applicable for solid state lighting. Accordingly, Ce and Dy activated NaLa(WO) and LiLa(WO) may be the promising materials for solid state lighting applications. [ABSTRACT FROM AUTHOR]

Energy transfer process at room temperature for cerium (sensitizer) oxalate single crystals doped with different concentrations (10, 13, 15, 17 and 20%) of praseodymium ions (activator) grown by hydro silica gel method has been evaluated. The analysis of energy level diagrams of cerium and praseodymium ions indicates that the energy gap between the sensitizer and the activator ions varies in a small range suggesting a possible energy transfer from the Ce to Pr. The emission and absorption spectra of these crystals were recorded. The overlapping of the absorption spectra of Pr and emission spectra of Ce at wavelengths 484 and 478 nm, respectively, strongly supports the possible energy transfer process in this system. From the absorption spectra, oscillator strength, electric dipole moment, branching ratio and Judd-Ofelt parameters of this system were evaluated by least square programming. The quantum efficiency, energy transfer probabilities and thermal properties have been studied. [ABSTRACT FROM AUTHOR]

Energy levels, with classifications and uncertainties, have been compiled for the spectra of the neutral atom and all positive ions of potassium (Z=19). Wavelengths with classifications, intensities, and transition probabilities are also tabulated. In addition, ground states and ionization energies are listed. For many ionization stages experimental data are available; however for those for which only theoretical calculations or fitted values exist, these are reported. [ABSTRACT FROM AUTHOR]

During the first measurement campaign of the EU FORMAT project in summer 2002 near Milan, northern Italy, ground-based scattered light differential optical absorption spectroscopy (DOAS) measurements were performed using a new multi-axis instrument. From the data set of this four week measurement period, the detailed analysis results of three days, 12-14 August, are presented exemplary. Slant column densities for formaldehyde (HCHO) and the oxygen dimer (O4) have been retrieved, employing fitting windows from 335 nm to 357 nm and 350 nm to 360 nm respectively. In order to convert slant into vertical columns radiative transfer calculations were perfomred using aerosol parameters derived from the actual O4 measurements. By analysing the measurements from different viewing directions (zenith, 4x off-axis) vertical profile information, and in particular mixing ratios for the boundary layer have been derived for the first time for HCHO with a multi-axis DOAS (MAX-DOAS) instrument. HCHO vertical columns are in the range of 5 to 20⋅1015 molec/cm² with an relative error of about 15%. This corresponds to HCHO mixing ratios in the boundary layer of 0.7 ppb to 4.2 ppb, which is in excellent agreement with simultaneous measurements from both a Hantzsch in-situ and a long-path DOAS instrument operated at the same place. [ABSTRACT FROM AUTHOR]

A spectrometer for measuring luminescence lifetimes has been developed. The design includes a bifurcated fibre optic cable for delivering the light from the source to the sample and from the sample to the detector. It uses a fast photomultiplier tube as the detector, a boxcar averager for data acquisition and a PC clone for data analysis. A nitrogen pumped dye laser is used as the light source and this has a pulse width of 1·2 ns. The spectrometer has been used to measure lifetimes from a minimum of 0·75 ns (rose bengal) to 597 μ s (solid uranyl nitrate hexahydrate). A study has been made of the effects of concentration and temperature on the decay of uranyl ions (UO) in aqueous solution. The decay is found to be biexponential, except at temperature above 60°C, where a three-component decay analysis gives the best results for matching the data to an Arrhenius Plot. The nature of the third emissive state, appearing at high temperatures is unknown and no spectroscopic state assignment has yet been made. [ABSTRACT FROM AUTHOR]