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Luminescence properties of phosphate phosphor Ba{sub 3}Y(PO{sub 4}){sub 3}:Sm{sup 3+}

A series of reddish orange-emitting phosphate phosphors Ba{sub 3}Y{sub 1−x}(PO{sub 4}){sub 3}:xSm{sup 3+}(0.01≤x≤0.20) were synthesized by solid-state reaction. X-ray diffraction and photoluminescence spectra were utilized to characterize the structure and luminescence properties of as-synthesized phosphors. The optimized phosphors Ba{sub 3}Y{sub 0.95}(PO{sub 4}){sub 3}:0.05Sm{sup 3+} present several excitation bands from 300 to 500 nm, and exhibit intense reddish orange-emitting properties. The energy transfer type between Sm{sup 3+} ions was confirmed as d–d interaction by using Van Uitert model. The chromatic properties of the typical sample Ba{sub 3}Y(PO{sub 4}){sub 3}:0.05Sm{sup 3+} phosphor have been found to have chromaticity coordinates of (0.583, 0.405), which are located in reddish orange region under the excitation of 401 nm. These results indicated that Ba{sub 3}Y(PO{sub 4}){sub 3}:Sm{sup 3+} phosphors have potential applications in the field of lighting and display due to their effective excitation in the near-ultraviolet range. - Graphical abstract: The color coordinates for 5 mol% Sm{sup 3+} doped Ba{sub 3}Y(PO{sub 4}){sub 3} phosphor were calculated to be (0.583, 0.405), which are located in reddish orange region under the excitation of 401 nm. The peaks of Ba{sub 3}Y{sub 0.95}(PO{sub 4}){sub 3}:0.05Sm{sup 3+} phosphor with the highest emission intensity at 600 nm are broader than those of Y{sub 2}O{sub 3}:Eu{sup 3+} and Y{sub 2}O{sub 2}S:Eu{sup 3+} phosphors. All these characteristics suggest that Ba{sub 3}Y(PO{sub 4}){sub 3}:Sm{sup 3+} phosphors are suitable for near-UV (370–410 nm) excitation and can be applicable to near UV-based WLEDs. ▪ - Highlights: • Different concentration Sm{sup 3+}-doped Ba{sub 3}Y(PO{sub 4}){sub 3} phosphors were fabricated by solid state method. • The optimized phosphors present the several excitation bands from 300 to 500 nm. • The Ba{sub 3}Y(PO{sub 4}){sub 3}:Sm{sup 3+} shows bright reddish orange emissions under 401 nm excitation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

INTERPRETING THE UNRESOLVED INTENSITY OF COSMOLOGICALLY REDSHIFTED LINE RADIATION

Intensity mapping experiments survey the spectrum of diffuse line radiation rather than detect individual objects at high signal-to-noise ratio. Spectral maps of unresolved atomic and molecular line radiation contain three-dimensional information about the density and environments of emitting gas and efficiently probe cosmological volumes out to high redshift. Intensity mapping survey volumes also contain all other sources of radiation at the frequencies of interest. Continuum foregrounds are typically ∼10{sup 2}–10{sup 3} times brighter than the cosmological signal. The instrumental response to bright foregrounds will produce new spectral degrees of freedom that are not known in advance, nor necessarily spectrally smooth. The intrinsic spectra of foregrounds may also not be well known in advance. We describe a general class of quadratic estimators to analyze data from single-dish intensity mapping experiments and determine contaminated spectral modes from the data themselves. The key attribute of foregrounds is not that they are spectrally smooth, but instead that they have fewer bright spectral degrees of freedom than the cosmological signal. Spurious correlations between the signal and foregrounds produce additional bias. Compensation for signal attenuation must estimate and correct this bias. A successful intensity mapping experiment will control instrumental systematics that spread variance into new modes, and it must observe a large enough volume that contaminant modes can be determined independently from the signal on scales of interest.

79 ASTRONOMY AND ASTROPHYSICS↗

Phosphorescence of Ce-doped Gd{sub 3}Al{sub 2}Ga{sub 3}O{sub 12} crystals studied using luminescence spectroscopy

Photoluminescence (PL) and thermally stimulated luminescence (TSL) properties of Ce-doped Gd{sub 3}Al{sub 2}Ga{sub 3}O{sub 12} (Ce:GAGG) crystals have been studied in the temperature range of 10–300 K under electron excitation from the 4f level to the 5d levels of Ce{sup 3+} ions. PL and TSL spectra commonly exhibit a prominent band around 2.31 eV, due to electron transitions from the lowest 5d (5d{sub 1}) level to the 4f levels. The intensity of the Ce{sup 3+} PL band is significantly changed with temperature under excitation from the lowest 4f level to a higher-lying 5d (5d{sub 2}) level, whereas it is scarcely changed under excitation from the 4f level to the 5d{sub 1} level. Such change correlates well with the appearance of TSL glow peaks at 84 and 175 K. The luminescence properties are apparently influenced by the thermal behavior of electrons trapped at some lattice site, but not by nonradiative processes of electrons starting from the 5d{sub 1} level. The phosphorescence process will be discussed using a phenomenological model based on the results obtained.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

THE UV/BLUE EFFECTS OF SPACE WEATHERING MANIFESTED IN S-COMPLEX ASTEROIDS. I. QUANTIFYING CHANGE WITH ASTEROID AGE

Evidence for the manifestation of space weathering in S-complex asteroids as a bluing of the UV/blue reflectance spectrum is extended using high resolution CCD reflectance spectra of 21 main-belt, 1 Mars-crossing, and 3 near-Earth asteroids covering a wavelength range of 320–620 nm. Demonstration of the transition of iron-bearing materials from volume scattering to surface (Fresnel) scattering is apparent as an abrupt downturn at wavelengths just short of 400 nm in reflectance spectra of fresh asteroid surfaces. The weathering away of this downturn is demonstrated by its absence in reflectance spectra of mature S-complex asteroids, consistent with an increase in npFe{sup 0} on the material's surface. Modeling of the effects of the addition of small amounts of npFe{sup 0} to particles from both a hypothetical mineral and a terrestrial basalt shows that evidence of the addition of 0.0001% npFe{sup 0} affects the reflectance at UV/blue wavelengths, while the addition of 0.01% is required to see the visible/near-infrared reddening and diminution of absorption features. Thus, the UV/blue reflectance characteristics allow earlier detection of the onset of space weathering effects. Combining UV/blue spectral characteristics of asteroids and ordinary chondrite meteorites with estimated ages of the young Datura family, we establish a method of dating asteroid surface ages during the early stages of space weathering. We demonstrate by dating the surface of NEA 163249 2002 GT to be 109 (±18) to 128 (±10) Kyr.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Photoluminescence of heterostructures containing an In{sub x}Ga{sub 1–x}As quantum well with a high in content at different excitation powers

The results of studies of the photoluminescence spectra of heterostructures containing an In{sub x}Ga{sub 1–x}As quantum well with a high In content x at different laser-radiation powers are reported. It is found that, as the radiation power density is increased, the luminescence spectrum of In{sub 0.70}Al{sub 0.30}As/In{sub 0.76}Ga{sub 0.24}As quantum-well heterostructures exhibits a decrease in the half-width and a shift of the peak to higher energies. It is shown that, for Al{sub 0.27}Ga{sub 0.73}As/In{sub 0.20}Ga{sub 0.80}As quantum-well heterostructures, no shift of the peak and no change in the shape of the spectrum is observed. It is established that the integrated photoluminescence intensity is related to the laser-radiation power density by a power law with the exponent α ≈ 1.3 for heterostructures with x ≈ 0.76, suggesting the predominantly excitonic character of the radiative recombination of charge carriers.

36 MATERIALS SCIENCE↗

THE FORMATION OF IRIS DIAGNOSTICS. VIII. IRIS OBSERVATIONS IN THE C ii 133.5 nm MULTIPLET

The C ii 133.5 nm multiplet has been observed by NASA’s Interface Region Imaging Spectrograph (IRIS) in unprecedented spatial resolution. The aims of this work are to characterize these new observations of the C ii lines, place them in context with previous work, and to identify any additional value the C ii lines bring when compared with other spectral lines. We make use of wide, long exposure IRIS rasters covering the quiet Sun and an active region. Line properties such as velocity shift and width are extracted from individual spectra and analyzed. The lines have a variety of shapes (mostly single-peak or double-peak), are strongest in active regions and weaker in the quiet Sun. The ratio between the 133.4 and 133.5 nm components is always less than 1.8, indicating that their radiation is optically thick in all locations. Maps of the C ii line widths are a powerful new diagnostic of chromospheric structures, and their line shifts are a robust velocity diagnostic. Compared with earlier quiet Sun observations, we find similar absolute intensities and mean line widths, but smaller redshifts; this difference can perhaps be attributed to differences in spectral resolution and spatial coverage. The C ii intensity maps are somewhat similar to those of transition region lines, but also share some features with chromospheric maps such as those from the Mg ii k line, indicating that they are formed between the upper chromosphere and transition region. C ii intensity, width, and velocity maps can therefore be used to gather additional information about the upper chromosphere.

79 ASTRONOMY AND ASTROPHYSICS↗

PROJECTED ROTATIONAL VELOCITIES AND STELLAR CHARACTERIZATION OF 350 B STARS IN THE NEARBY GALACTIC DISK

Projected rotational velocities (v sin i) are presented for a sample of 350 early B-type main-sequence stars in the nearby Galactic disk. The stars are located within {approx}1.5 kpc from the Sun, and the great majority within 700 pc. The analysis is based on high-resolution spectra obtained with the MIKE spectrograph on the Magellan Clay 6.5 m telescope at the Las Campanas Observatory in Chile. Spectral types were estimated based on relative intensities of some key line absorption ratios and comparisons to synthetic spectra. Effective temperatures were estimated from the reddening-free Q index, and projected rotational velocities were then determined via interpolation on a published grid that correlates the synthetic FWHM of the He I lines at 4026, 4388 and 4471 A with v sin i. As the sample has been selected solely on the basis of spectral types, it contains a selection of B stars in the field, in clusters, and in OB associations. The v sin i distribution obtained for the entire sample is found to be essentially flat for v sin i values between 0 and 150 km s{sup -1}, with only a modest peak at low projected rotational velocities. Considering subsamples of stars, there appears to be a gradation in the v sin i distribution with the field stars presenting a larger fraction of the slow rotators and the cluster stars distribution showing an excess of stars with v sin i between 70 and 130 km s{sup -1}. Furthermore, for a subsample of potential runaway stars we find that the v sin i distribution resembles the distribution seen in denser environments, which could suggest that these runaway stars have been subject to dynamical ejection mechanisms.

79 ASTRONOMY AND ASTROPHYSICS↗

Photospheric Emission in the Joint GBM and Konus Prompt Spectra of GRB 120323A

GRB 120323A is a very intense short gamma-ray burst (GRB) detected simultaneously during its prompt gamma-ray emission phase with the Gamma-Ray Burst Monitor (GBM) on board the Fermi Gamma-Ray Space Telescope and the Konus experiment on board the Wind satellite. GBM and Konus operate in the kiloelectronvolt - megaelectronvolt regime; however, the GBM range is broader toward both the low and the high parts of the gamma-ray spectrum. Analyses of such bright events provide a unique opportunity to check the consistency of the data analysis as well as cross-calibrate the two instruments. We performed time-integrated and coarse time-resolved spectral analysis of GRB 120323A prompt emission. We conclude that the analyses of GBM and Konus data are only consistent when using a double-hump spectral shape for both data sets; in contrast, the single hump of the empirical Band function, traditionally used to fit GRB prompt emission spectra, leads to significant discrepancies between GBM and Konus analysis results. Our two-hump model is a combination of a thermal-like and a non-thermal component. We interpret the first component as a natural manifestation of the jet photospheric emission.

Guiriec, S.↗

ESTIMATION OF DISTANCES TO STARS WITH STELLAR PARAMETERS FROM LAMOST

We present a method to estimate distances to stars with spectroscopically derived stellar parameters. The technique is a Bayesian approach with likelihood estimated via comparison of measured parameters to a grid of stellar isochrones, and returns a posterior probability density function for each star’s absolute magnitude. This technique is tailored specifically to data from the Large Sky Area Multi-object Fiber Spectroscopic Telescope (LAMOST) survey. Because LAMOST obtains roughly 3000 stellar spectra simultaneously within each ∼5° diameter “plate” that is observed, we can use the stellar parameters of the observed stars to account for the stellar luminosity function and target selection effects. This removes biasing assumptions about the underlying populations, both due to predictions of the luminosity function from stellar evolution modeling, and from Galactic models of stellar populations along each line of sight. Using calibration data of stars with known distances and stellar parameters, we show that our method recovers distances for most stars within ∼20%, but with some systematic overestimation of distances to halo giants. We apply our code to the LAMOST database, and show that the current precision of LAMOST stellar parameters permits measurements of distances with ∼40% error bars. This precision should improve as the LAMOST data pipelines continue to be refined.

79 ASTRONOMY AND ASTROPHYSICS↗

TIME-SERIES SPECTROSCOPY OF THE ECLIPSING BINARY Y CAM WITH A PULSATING COMPONENT

We present the physical properties of the semi-detached Algol-type eclipsing binary Y Cam based on high resolution spectra obtained using the Bohyunsan Optical Echelle Spectrograph. This is the first spectroscopic monitoring data obtained for this interesting binary system, which has a δ Sct-type pulsating component. We obtained a total of 59 spectra over 14 nights from 2009 December to 2011 March. Double-lined spectral features from the hot primary and cool secondary components were well identified. We determined the effective temperatures of the two stars to be T{sub eff,1} = 8000 ± 250 K and T{sub eff,2} = 4629 ± 150 K. The projected rotational velocities are v{sub 1}sin i{sub 1} = 51 ± 4 km s{sup −1} and v{sub 2}sin i{sub 2} = 50 ± 10 km s{sup −1}, which are very similar to a synchronous rotation with the orbital motion. Physical parameters of each component were derived by analyzing our radial velocity data together with previous photometric light curves from the literature. The masses and radii are M{sub 1} = 2.08 ± 0.09 M{sub ⊙}, M{sub 2} = 0.48 ± 0.03 M{sub ⊙}, R{sub 1} = 3.14 ± 0.05 R{sub ⊙}, and R{sub 2} = 3.33 ± 0.05 R{sub ⊙}, respectively. A comparison of these parameters with the theoretical evolution tracks showed that the primary component is located between the zero-age main sequence and the terminal-age main sequence, while the low-mass secondary is noticeably evolved. This indicates that the two components have experienced mass exchange with each other and the primary has undergone an evolution process different from that of single δ Sct-type pulsators.

79 ASTRONOMY AND ASTROPHYSICS↗

IMPROVING COSMOLOGICAL DISTANCE MEASUREMENTS USING TWIN TYPE IA SUPERNOVAE

We introduce a method for identifying “twin” Type Ia supernovae (SNe Ia) and using them to improve distance measurements. This novel approach to SN Ia standardization is made possible by spectrophotometric time series observations from the Nearby Supernova Factory (SNfactory). We begin with a well-measured set of SNe, find pairs whose spectra match well across the entire optical window, and then test whether this leads to a smaller dispersion in their absolute brightnesses. This analysis is completed in a blinded fashion, ensuring that decisions made in implementing the method do not inadvertently bias the result. We find that pairs of SNe with more closely matched spectra indeed have reduced brightness dispersion. We are able to standardize this initial set of SNfactory SNe to 0.083 ± 0.012 mag, implying a dispersion of 0.072 ± 0.010 mag in the absence of peculiar velocities. We estimate that with larger numbers of comparison SNe, e.g., using the final SNfactory spectrophotometric data set as a reference, this method will be capable of standardizing high-redshift SNe to within 0.06–0.07 mag. These results imply that at least 3/4 of the variance in Hubble residuals in current SN cosmology analyses is due to previously unaccounted-for astrophysical differences among the SNe.

79 ASTRONOMY AND ASTROPHYSICS↗

TYPE IIn SUPERNOVA SN 2010jl: OPTICAL OBSERVATIONS FOR OVER 500 DAYS AFTER EXPLOSION

We present extensive optical observations of a Type IIn supernova (SN IIn) 2010jl for the first 1.5 years after its discovery. The UBVRI light curves demonstrated an interesting two-stage evolution during the nebular phase, which almost flatten out after about 90 days from the optical maximum. SN 2010jl has one of the highest intrinsic H{alpha} luminosities ever recorded for an SN IIn, especially at late phase, suggesting a strong interaction of SN ejecta with the dense circumstellar material (CSM) ejected by the progenitor. This is also indicated by the remarkably strong Balmer lines persisting in the optical spectra. One interesting spectral evolution about SN 2010jl is the appearance of asymmetry of the Balmer lines. These lines can be well decomposed into a narrow component and an intermediate-width component. The intermediate-width component showed a steady increase in both strength and blueshift with time until t {approx} 400 days after maximum, but it became less blueshifted at t {approx} 500 days, when the line profile appeared relatively symmetric again. Owing to the fact that a pure reddening effect will lead to a sudden decline of the light curves and a progressive blueshift of the spectral lines, we therefore propose that the asymmetric profiles of H lines seen in SN 2010jl are unlikely due to the extinction by newly formed dust inside the ejecta, contrary to the explanation by some early studies. Based on a simple CSM-interaction model, we speculate that the progenitor of SN 2010jl may suffer a gigantic mass loss ({approx}30-50 M{sub Sun }) a few decades before explosion. Considering a slow-moving stellar wind (e.g., {approx}28 km s{sup -1}) inferred for the preexisting, dense CSM shell and the extremely high mass-loss rate (1-2 M{sub Sun} yr{sup -1}), we suggest that the progenitor of SN 2010jl might have experienced a red supergiant stage and may explode finally as a post-red supergiant star with an initial mass above 30-40 M{sub Sun }.

79 ASTRONOMY AND ASTROPHYSICS↗

The growth of sulfur adlayers on Au(100)

We have studied the growth of S layers adsorbed on Au(100) with low-energy electron diffraction (LEED), X-ray photoemission spectra (XPS), and scanning tunneling microscope (STM). Three phases of S/Au(100)—(2 × 2), trimer, and c(2 × 4)—are identified; the latter two are not previously reported. A dose of S{sub 2} at 300 K transformed Au(100)-(5 × 20) initially into the (2 × 2) phase and formed the c(2 × 4) phase at a saturation coverage. The STM results show that monolayer Au islands formed during the initial S dose and remained throughout the growth, resulting in a rough c(2 × 4) surface. We show that a highly ordered c(2 × 4) phase can be obtained with a flat (2 × 2) phase as an intermediate step during growth. Based on the evolution of XPS and STM images with varied S{sub 2} dose, the components of S 2p are assigned and structural models for the various S/Au(100) phases are proposed. In the (2 × 2) phase, one S atom resides on a four-fold hollow site in each (2 × 2) unit cell, corresponding to a S coverage of 0.25 ML; in the trimer phase, three S atoms form a trimer residing on a four-fold hollow site in each (2 × 2) unit cell, corresponding to a S coverage of 0.75 ML; in the c(2 × 4) phase, there are five S atoms in each primitive unit cell of c(2 × 4); three of them form a trimer residing on a four-fold hollow site, and the other two form a dimer located on the top of the trimer, corresponding to a nominal S coverage of 1.25 ML. With the proposed structural models, the growth of S on Au(100) at 300 K is described in detail.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

The eleventh and twelfth data release of the Sloan Digital Sky Survey: Final data from SDSS-III

The third generation of the Sloan Digital Sky Survey (SDSS-III) took data from 2008 to 2014 using the original SDSS wide-field imager, the original and an upgraded multi-object fiber-fed optical spectrograph, a new near-infrared high-resolution spectrograph, and a novel optical interferometer. All of the data from SDSS-III are now made public. In particular, this paper describes Data Release 11 (DR11) including all data acquired through 2013 July, and Data Release 12 (DR12) adding data acquired through 2014 July (including all data included in previous data releases), marking the end of SDSS-III observing. Relative to our previous public release (DR10), DR12 adds one million new spectra of galaxies and quasars from the Baryon Oscillation Spectroscopic Survey (BOSS) over an additional 3000 deg 2 of sky, more than triples the number of H-band spectra of stars as part of the Apache Point Observatory (APO) Galactic Evolution Experiment (APOGEE), and includes repeated accurate radial velocity measurements of 5500 stars from the Multi-object APO Radial Velocity Exoplanet Large-area Survey (MARVELS). The APOGEE outputs now include the measured abundances of 15 different elements for each star. In total, SDSS-III added 5200 deg 2 of ugriz imaging; 155,520 spectra of 138,099 stars as part of the Sloan Exploration of Galactic Understanding and Evolution 2 (SEGUE-2) survey; 2,497,484 BOSS spectra of 1,372,737 galaxies, 294,512 quasars, and 247,216 stars over 9376 deg 2 ; 618,080 APOGEE spectra of 156,593 stars; and 197,040 MARVELS spectra of 5513 stars. Since its first light in 1998, SDSS has imaged over 1/3 of the Celestial sphere in five bands and obtained over five million astronomical spectra.

79 ASTRONOMY AND ASTROPHYSICS↗

Characterization of dissolved organic matter in landfill leachate during the combined treatment process of air stripping, Fenton, SBR and coagulation

Highlights: • DOM fractions spectra analysis during the whole treatment process. • Efficient method was achieved to remove organic matters in landfill leachate. • Molecular weight distribution and fractions were discussed. - Abstract: A combined treatment process of air stripping + Fenton + sequencing batch reactor (SBR)+ coagulation was performed to remove the pollutants in landfill leachate. Molecular weight (MW) distribution and fractions of dissolved organic matter (DOM) were discussed to study the characteristics. The experiment showed that the removal rate of chemical oxygen demand (COD), five day biological oxygen demand (BOD{sub 5}) and ammonia nitrogen (NH{sub 3}−N) by the combined process were 92.8%, 87.8% and 98.0%, respectively. Humic acid (HA) and fulvic acid (FA) were the main fractions in raw leachate with 81.8% of the total COD concentration, while hydrophilic organic matter (HyI) was the dominant fraction in the final effluent of the combined process with 63.5% of the total COD concentration. After the combined treatment process, the removal rate of DOM and fractions HA, FA, HyI were 91.9%, 97.1%, 95.8% and 71.7%, respectively. Organic matters of MW < 2 k and MW > 100 k were removed with 90.5% and 97.9% COD concentration after the treatment. The ultraviolet–visible spectra (UV–vis), Fourier transform infrared spectra (FTIR) and three-dimensional excitation-emission matrices spectra (EEMs) indicated that benzene materials and phenol compounds were preferentially removed in air stripping. High MW matters, aromatic rings, conjugated moieties and some functional groups were mainly removed by Fenton. While small MW fractions, carboxylic acids, alcohols and protein-like materials were preferentially biodegraded via SBR. Fulvic-like and humic-like materials were mainly destroyed via Fenton oxidation and coagulation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Low-energy electro- and photo-emission spectroscopy of GaN materials and devices

In hot-electron semiconductor devices, carrier transport extends over a wide range of conduction states, which often includes multiple satellite valleys. Electrical measurements can hardly give access to the transport processes over such a wide range without resorting to models and simulations. An alternative experimental approach however exists which is based on low-energy electron spectroscopy and provides, in a number of cases, very direct and selective information on hot-electron transport mechanisms. Recent results obtained in GaN crystals and devices by electron emission spectroscopy are discussed. Using near-band-gap photoemission, the energy position of the first satellite valley in wurtzite GaN is directly determined. By electro-emission spectroscopy, we show that the measurement of the electron spectrum emitted from a GaN p-n junction and InGaN/GaN light-emitting diodes (LEDs) under electrical injection of carriers provides a direct observation of transport processes in these devices. In particular, at high injected current density, high-energy features appear in the electro-emission spectrum of the LEDs showing that Auger electrons are being generated in the active region. These measurements allow us identifying the microscopic mechanism responsible for droop which represents a major hurdle for widespread adoption of solid-state lighting.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Modification of opto-electronic properties of ZnO by incorporating metallic tin for buffer layer in thin film solar cells

In this report, the effect of incorporation of metallic tin (Sn) on opto-electronic properties of ZnO thin films is presented. ZnO thin films were deposited through ‘automated chemical spray pyrolysis’ (CSP) technique; later different quantities of ‘Sn’ were evaporated on it and subsequently annealed. Vacuum annealing showed a positive effect on crystallinity of films. Creation of sub band gap levels due to ‘Sn’ diffusion was evident from the absorption and PL spectra. The tin incorporated films showed good photo response in visible region. Tin incorporated ZnO thin films seem to satisfy the desirable criteria for buffer layer in thin film solar cells.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

Solar flare impulsive phase emission observed with SDO/EVE

Differential emission measures (DEMs) during the impulsive phase of solar flares were constructed using observations from the EUV Variability Experiment (EVE) and the Markov-Chain Monte Carlo method. Emission lines from ions formed over the temperature range log T{sub e} = 5.8-7.2 allow the evolution of the DEM to be studied over a wide temperature range at 10 s cadence. The technique was applied to several M- and X-class flares, where impulsive phase EUV emission is observable in the disk-integrated EVE spectra from emission lines formed up to 3-4 MK and we use spatially unresolved EVE observations to infer the thermal structure of the emitting region. For the nine events studied, the DEMs exhibited a two-component distribution during the impulsive phase, a low-temperature component with peak temperature of 1-2 MK, and a broad high-temperature component from 7 to 30 MK. A bimodal high-temperature component is also found for several events, with peaks at 8 and 25 MK during the impulsive phase. The origin of the emission was verified using Atmospheric Imaging Assembly images to be the flare ribbons and footpoints, indicating that the constructed DEMs represent the spatially average thermal structure of the chromospheric flare emission during the impulsive phase.

79 ASTRONOMY AND ASTROPHYSICS↗