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Stellar ultraviolet (UV) emission serves as a crucial indicator for estimating magnetic activity and evaluating the habitability of exoplanets orbiting stars. In this paper, we present a straightforward method to derive stellar photospheric UV emission for F to M main-sequence stars. By using PARSEC models, we establish relations between near-UV (NUV) and far-UV (FUV) magnitudes from the Galaxy Evolution Explorer, NUV magnitudes from the China Space Station Telescope, and stellar effective temperatures and Gaia blue photometer–red photometer colors for different metallicities. Together with the observed sample, we find that for NUV emission, the photospheric contribution to the observed flux is less than 20% for M stars, around 10%–70% for K stars, and in a range from 30% to 85% for G and F stars. For FUV emission, the photospheric contribution is less than 10−6 for M stars, below 10−4 for K stars, around 10−4–10% for G stars, and between 6% and 50% for F stars. Our work enables the simple and effective determination of stellar excess UV emission and the exploration of magnetic activity. [ABSTRACT FROM AUTHOR]

Blazars, the peculiar class of active galactic nuclei, are known to show flux variations across the accessible electromagnetic spectrum. Though they have been studied extensively for their flux variability characteristics across wavelengths, information on their ultraviolet (UV) flux variations on timescales of hours is very limited. Here, we present the first UV flux variability study on intraday timescales of a sample of ten blazars comprising two flat-spectrum radio quasars (FSRQs) and eight BL Lacertae objects (BL Lacs). These objects, spanning a redshift (z) range of 0.034 ≤ z ≤ 1.003, were observed in the far-UV (1300−1800 Å) and near-UV (2000−3000 Å) wavebands using the ultraviolet imaging telescope on board AstroSat. UV flux variations on timescales of hours were detected in nine sources out of the observed ten blazars. The spectral variability analysis showed a bluer-when-brighter trend with no difference in the UV spectral variability behavior between the studied sample of FSRQs and BL Lacs. The observed UV flux and spectral variability in our sample of both FSRQs and BL Lacs revealed that the observed UV emission in them is dominated by jet synchrotron process. [ABSTRACT FROM AUTHOR]

We measure the bolometric luminosity of a complete and unbiased 12 μ m-selected sample of active galactic nuclei (AGN) in the local Universe. For each galaxy, we used a 10-band radio-to-X-ray spectral energy distribution (SED) to isolate the genuine AGN continuum in each band, including subarcsecond measurements where available, and correcting those contaminated by the host galaxy. We derive the median SED of Seyfert type 1 AGN, Seyferts with hidden broad lines (HBLs), Seyferts of type 2, and LINER nuclei in our sample. The median Seyfert 1 SED shows the characteristic blue bump feature in the UV, but nevertheless, the largest contribution to the bolometric luminosity comes from the IR and X-ray continua. The median SEDs of both HBL and type 2 AGN are affected by starlight contamination in the optical/UV. The median SED of HBL AGN is consistent with that of Seyfert 1s, when an extinction of A V ∼ 1.2 mag is applied. The comprehensive SEDs allowed us to measure accurate bolometric luminosities and derive robust bolometric corrections for the different tracers. The 12 μ m and K -band nuclear luminosities have good linear correlations with the bolometric luminosity, similar to those in the X-rays. We derive bolometric corrections for either continuum bands (K band, 12 μ m, 2–10 keV, and 14–195 keV) or narrow emission lines (mid-IR high-ionization lines of [O iv ] and [Ne v ] and optical [O iii ] 5007 Å) as well as for combinations of IR continuum and line emission. A combination of continuum plus line emission accurately predicts the bolometric luminosity up to quasar luminosities (∼1046 erg s−1). [ABSTRACT FROM AUTHOR]

Three fields in the outskirts of the Small Magellanic Cloud were observed by the UltraViolet Imaging Telescope (UVIT) on board AstroSat, between 2017 December 31 and 2018 January 1. The observations were carried out on a total of seven filters, three in the far-ultraviolet (FUV; 1300–1800 Å) band and four in the near-ultraviolet (NUV; 2000–3000 Å) band. We carried out photometry of these observations that have a spatial resolution better than 1.″5. We present here the first results of this work, which is a matched catalog of 11,241 sources detected in three FUV and four NUV wavelengths. We make the catalog available online, which would be of use to the astronomical community to address a wide variety of astrophysical problems. We provide an expression to estimate the total count rate in the full point-spread function of UVIT that also incorporates the effect of saturation. [ABSTRACT FROM AUTHOR]

We present the first far-UV (FUV) imaging results of the intermediate-age Galactic open cluster NGC 2818 that has a planetary nebula (PN) within the field using images taken from the Ultra Violet Imaging Telescope (UVIT) aboard AstroSat. We identify cluster members by combining UVIT-detected sources with Gaia EDR3 data. We detect four bright and hot blue straggler stars (BSSs) and two yellow straggler stars (YSSs) based on their location in optical and FUV–optical color–magnitude diagrams. Based on the parameters estimated using spectral energy distributions, we infer that BSSs are either collisional products or might have undetectable white dwarf (WD) companions. Our photometric analysis of YSSs confirms their binarity, consistent with the spectroscopic results. We find YSSs to be formed through a mass-transfer scenario and the hot components are likely to be A-type subdwarfs. A comparison of the radial velocity, Gaia EDR3 proper motion of the PN with the cluster, and reddening toward the PN and the cluster does not rule out the membership of the PN. Comparing the central star's position with theoretical post‐AGB (pAGB) models suggest that it has already entered the WD cooling phase, and its mass is deduced to be ∼0.66 M ⊙. The corresponding progenitor mass turns out to be ∼2.1 M ⊙, comparable to the turn-off mass of the cluster, implying that the progenitor could have formed in the cluster. We suggest that the NGC 2818 might be one of the few known clusters to host a PN, providing a unique opportunity to test stellar evolution models. [ABSTRACT FROM AUTHOR]

Stellar ultraviolet (UV) emission serves as a crucial indicator for estimating magnetic activity and evaluating the habitability of exoplanets orbiting stars. In this paper, we present a straightforward method to derive stellar photospheric UV emission for F to M main-sequence stars. By using PARSEC models, we establish relations between near-UV (NUV) and far-UV (FUV) magnitudes from the Galaxy Evolution Explorer, NUV magnitudes from the China Space Station Telescope, and stellar effective temperatures and Gaia blue photometer–red photometer colors for different metallicities. Together with the observed sample, we find that for NUV emission, the photospheric contribution to the observed flux is less than 20% for M stars, around 10%–70% for K stars, and in a range from 30% to 85% for G and F stars. For FUV emission, the photospheric contribution is less than 10 ^−6 for M stars, below 10 ^−4 for K stars, around 10 ^−4 –10% for G stars, and between 6% and 50% for F stars. Our work enables the simple and effective determination of stellar excess UV emission and the exploration of magnetic activity.

The changes in colors across a galaxy are intimately connected to the galaxy’s formation, growth, quenching history, and dust content. A particularly important epoch in the growth of galaxies is near z ∼ 2, often referred to as “cosmic noon,” where galaxies on average reach the peak of their star formation. We study a population of 125 cluster galaxies at z ∼ 1.6 in three Hubble Space Telescope filters, F475W, F625W, and F160W, roughly corresponding to the rest-frame far-ultraviolet, near-ultraviolet, and r band, respectively. By comparing to a control sample of 200 field galaxies at similar redshift, we reveal clear, statistically significant differences in the overall spatially resolved colors and color gradients in galaxies across these two different environments. On average, cluster galaxies have redder ultraviolet colors in both the inner and outer regions bounded by r _50 , as well as an overall wider dispersion of outside-in color gradients. The presence of these observed differences, along with evidence from ancillary data from previous studies, strongly suggests that the environment drives these population-level color differences, by affecting the stellar populations and/or dust content.

Blazars, the peculiar class of active galactic nuclei, are known to show flux variations across the accessible electromagnetic spectrum. Though they have been studied extensively for their flux variability characteristics across wavelengths, information on their ultraviolet (UV) flux variations on timescales of hours is very limited. Here, we present the first UV flux variability study on intraday timescales of a sample of ten blazars comprising two flat-spectrum radio quasars (FSRQs) and eight BL Lacertae objects (BL Lacs). These objects, spanning a redshift ( z ) range of 0.034 ≤ z ≤ 1.003, were observed in the far-UV (1300−1800 Å) and near-UV (2000−3000 Å) wavebands using the ultraviolet imaging telescope on board AstroSat. UV flux variations on timescales of hours were detected in nine sources out of the observed ten blazars. The spectral variability analysis showed a bluer-when-brighter trend with no difference in the UV spectral variability behavior between the studied sample of FSRQs and BL Lacs. The observed UV flux and spectral variability in our sample of both FSRQs and BL Lacs revealed that the observed UV emission in them is dominated by jet synchrotron process.

We present a catalog of 71,364 pointlike UV sources with Sloan Digital Sky Survey (SDSS) photometry and GALEX far-UV (FUV)−near-UV (NUV) ≤0.1 mag. The limit corresponds to stellar T _eff ≳15,000−20,000 K, slightly depending on gravity but nearly reddening independent for Milky Way−type dust. Most sources are hot white dwarfs (WDs) and subdwarfs. Comparing the spectral energy distribution (SED; GALEX FUV, NUV, SDSS u,g,r,i,z ) of 35,294 sources having good photometry with colors of stellar models and known objects, we identify 12,404 ± ${}_{1267}^{1871}$ binary hot-compact stars with a cooler, less-evolved companion (with a possible 8%–15% contamination by low-redshift QSOs), and 22,848 ± ${}_{3853}^{1267}$ single-star candidates. Single-star counts are an upper limit because pairs of similar stars have single-star-like SEDs, and hot WDs with main-sequence companions of certain types (depending on the WD’s radius) are missed or counted as single in the available wavelength range and selection. The catalog offers unique leverage for identifying hot WDs, elusive at longer wavelengths when a cooler, larger companion dominates optical–IR fluxes: 51% of the binary-star and 20% of the single-star candidates are previously unknown objects. Gaia DR3 provides a parallax with error ≤20% for 34% of the binary-star candidates and 45% of single-star candidates, allowing T _eff , E _B _− _V , radius, and L _bol to be derived from SED analysis. The binary-candidate sample usefully expands the overall current binary-WD census to subpopulations elusive to Gaia and to other searches. The binary fraction among this specific sample of hot compact objects, albeit with the mentioned biases, b _f ≳ 46%, compared with that of their progenitors (>80%–50% for mass range 8−1 M _⊙ , according to M. Moe), implies a lower merging rate than found for massive stars by H. Sana et al.

We present results from simultaneous far-ultraviolet (FUV) and near-ultraviolet (NUV) observations of T Tauri stars (TTSs) in the Taurus molecular cloud with UVIT/AstroSat. This is the very first UVIT study of TTSs. From the spectral energy distribution of TTSs from FUV to IR, we show that classical TTSs (CTTSs) emit significantly higher UV excess compared to weak-line TTSs (WTTSs). The equivalent blackbody temperatures corresponding to the UV excess in CTTSs (>10 ^4 K) are also found to be relatively higher than those in WTTSs (10 ^7 ) and NUV (>10 ^3 ) bands, while WTTSs show strong excess only in the FUV (≲10 ^5 ), suggesting that excess emission in the NUV can be used as a tool to classify the TTSs. We also find a linear correlation between UV luminosity (a primary indicator of mass accretion) and H α luminosity (a secondary indicator of mass accretion) with a slope of 1.20 ± 0.22 and intercept of 2.16 ± 0.70.

M-type stars are crucial for stellar activity studies because they cover two types of magnetic dynamos and are particularly intriguing for habitability studies due to their abundance and long lifespans during the main-sequence stage. In this paper, we used the LAMOST DR9 catalog and the GALEX UV archive data to investigate the chromospheric and UV activities of M-type stars. All the chromospheric and UV activity indices clearly show that the saturated and unsaturated regimes, and the well-known activity–rotation relation, are consistent with previous studies. Both the FUV and NUV activity indices exhibit a single-peaked distribution, while the H α and Ca ii H&K indices show a distinct double-peaked distribution. The gap between these peaks suggests a rapid transition from a saturated population to an unsaturated one. The smoothly varying distributions of different subtypes suggest a rotation-dependent dynamo for both early-type (partly convective) to late-type (fully convective) M stars. We identified a group of stars with high UV activity above the saturation regime (log ${R}_{\mathrm{NUV}}^{{\prime} }\gt -2.5$ ) but low chromospheric activity, and the underlying reason is unknown. By calculating the continuously habitable zone and the UV habitable zone for each star, we found that about 70% stars in the total sample and 40% stars within 100 pc are located in the overlapping region of these two habitable zones, indicating that a number of M stars are potentially habitable. Finally, we examined the possibility of UV activity studies of M stars using the China Space Station Telescope.

We measure the bolometric luminosity of a complete and unbiased 12 μ m-selected sample of active galactic nuclei (AGN) in the local Universe. For each galaxy, we used a 10-band radio-to-X-ray spectral energy distribution (SED) to isolate the genuine AGN continuum in each band, including subarcsecond measurements where available, and correcting those contaminated by the host galaxy. We derive the median SED of Seyfert type 1 AGN, Seyferts with hidden broad lines (HBLs), Seyferts of type 2, and LINER nuclei in our sample. The median Seyfert 1 SED shows the characteristic blue bump feature in the UV, but nevertheless, the largest contribution to the bolometric luminosity comes from the IR and X-ray continua. The median SEDs of both HBL and type 2 AGN are affected by starlight contamination in the optical/UV. The median SED of HBL AGN is consistent with that of Seyfert 1s, when an extinction of A _V ∼ 1.2 mag is applied. The comprehensive SEDs allowed us to measure accurate bolometric luminosities and derive robust bolometric corrections for the different tracers. The 12 μ m and K -band nuclear luminosities have good linear correlations with the bolometric luminosity, similar to those in the X-rays. We derive bolometric corrections for either continuum bands ( K band, 12 μ m, 2–10 keV, and 14–195 keV) or narrow emission lines (mid-IR high-ionization lines of [O iv ] and [Ne v ] and optical [O iii ] 5007 Å) as well as for combinations of IR continuum and line emission. A combination of continuum plus line emission accurately predicts the bolometric luminosity up to quasar luminosities (∼10 ^46 erg s ^−1 ).

We present the the new Swift/UVOT+MaNGA (SwiM) catalog (SwiM_v4.1). SwiM_v4.1 is designed to study star formation and dust attenuation within nearby galaxies given the unique overlap of Swift/UVOT near-ultraviolet (NUV) imaging and MaNGA integral field optical spectroscopy. SwiM_v4.1 comprises 559 objects, ∼4 times more than the original SwiM catalog (SwiM_v3.1), spans the redshift range z ≈ 0.0002–0.1482, and provides a more diverse and rich sample. Approximately 5% of the final MaNGA sample is included in SwiM_v4.1, and 42% of the SwiM_v4.1 galaxies are cross-listed with other well-known catalogs. We present the same data as SwiM_v3.1, including UVOT images, Sloan Digital Sky Survey (SDSS) images, and MaNGA emission-line and spectral index maps with the same pixel size and angular resolution for each galaxy, and a file containing galaxy and observational properties. We designed SwiM_v4.1 to be unbiased, which resulted in some objects having low signal-to-noise ratios in their MaNGA or Swift data. We addressed this by providing a new file containing the fraction of science-ready pixels in each MaNGA emission-line map, and the integrated flux and inverse variance for all three NUV filters. The uniform angular resolution and sampling in SwiM_v4.1 will help answer a number of scientific questions, including constraining quenching and attenuation in the local Universe and studying the effects of black hole feedback. The galaxy maps, catalog files, and their associated data models are publicly released on the SDSS website (a description of the SwiM VAC is provided at https://www.sdss4.org/dr17/data_access/value-added-catalogs/?vac_id=swift-manga-value-added-catalog , and the data are stored on the SDSS Science Archive Server at https://data.sdss.org/sas/dr17/manga/swim/v4.1/ ).

Recently, slowly cooling white dwarfs (WDs) are a new class of WD that have been identified in two globular clusters (namely M13 and NGC 6752), showing a horizontal branch (HB) morphology with an extended blue tail. The cooling rate of these WDs is reduced by stable thermonuclear hydrogen burning in their residual envelope, and they are thought to originate by stars that populate the blue tail of the HB and then skip the asymptotic giant branch phase. Consistently, no evidence of such kind of WDs has been found in M3, a similar cluster with no blue extension of the HB. To further explore this phenomenon, we took advantage of deep photometric data acquired with the Hubble Space Telescope in the near-ultraviolet and investigated the bright portion of the WD cooling sequence in M5, another Galactic globular cluster with HB morphology similar to M3. The normalized WD luminosity function derived in M5 was found to be impressively similar to that observed in M3, in agreement with the fact that the stellar mass distribution along the HB of these two systems is almost identical. The comparison with theoretical predictions is consistent with the fact that the cooling sequence in this cluster is populated by canonical (fast cooling) WDs. Thus, the results presented in this paper provide further support to the scenario proposing a direct causal connection between the slow cooling WD phenomenon and the horizontal branch morphology of the host stellar cluster.

We present the first far-UV (FUV) imaging results of the intermediate-age Galactic open cluster NGC 2818 that has a planetary nebula (PN) within the field using images taken from the Ultra Violet Imaging Telescope (UVIT) aboard AstroSat. We identify cluster members by combining UVIT-detected sources with Gaia EDR3 data. We detect four bright and hot blue straggler stars (BSSs) and two yellow straggler stars (YSSs) based on their location in optical and FUV–optical color–magnitude diagrams. Based on the parameters estimated using spectral energy distributions, we infer that BSSs are either collisional products or might have undetectable white dwarf (WD) companions. Our photometric analysis of YSSs confirms their binarity, consistent with the spectroscopic results. We find YSSs to be formed through a mass-transfer scenario and the hot components are likely to be A-type subdwarfs. A comparison of the radial velocity, Gaia EDR3 proper motion of the PN with the cluster, and reddening toward the PN and the cluster does not rule out the membership of the PN. Comparing the central star’s position with theoretical post‐AGB (pAGB) models suggest that it has already entered the WD cooling phase, and its mass is deduced to be ∼0.66 M _⊙ . The corresponding progenitor mass turns out to be ∼2.1 M _⊙ , comparable to the turn-off mass of the cluster, implying that the progenitor could have formed in the cluster. We suggest that the NGC 2818 might be one of the few known clusters to host a PN, providing a unique opportunity to test stellar evolution models.

We estimate the UV continuum slope ( β ) of 465 galaxies (with luminosities of 0.028–3.3 ${L}_{z=0.5}^{* }$ ) in the Great Observatories Origins Survey Northern field in the redshift range z = 0.40–0.75. We use two AstroSat/UVIT (N242W, N245M) bands, two Hubble Space Telescope (F275W, F336W) bands, and a KPNO ( U ) band to sample the UV continuum slope of selected galaxies between 1215 and 2600 Å. The mean (median) and 1 σ scatter in the observed β are found to be −1.33 ± 0.07 ( − 1.32) and 0.60 within the considered redshift range. We do not find any significant evolution in the mean β within our redshift window. Our measurements add new data points to the global β – z relation in the least-explored redshift regime, further reinforcing the gradual reddening of galaxy UV continuum with cosmic time. We notice no strong consistent trend between β and M _1500 for the entire luminosity range −21 < M _1500 < − 15 mag. However, the majority of the most-luminous galaxies ( M _1500 < − 19 mag) are found to have relatively redder slopes. Using UVIT, we detect galaxies as faint as M _1500 = − 15.6 mag (i.e., 0.028 ${L}_{z=0.5}^{* }$ ). The faintest galaxies ( M _1500 > − 16 mag) tend to be redder, which indicates they were less actively forming stars during this cosmic time interval. Our study highlights the unique capability of UVIT near-UV imaging to characterize the rest-frame far-UV properties of galaxies at redshift z ∼ 0.5.

Three fields in the outskirts of the Small Magellanic Cloud were observed by the UltraViolet Imaging Telescope (UVIT) on board AstroSat, between 2017 December 31 and 2018 January 1. The observations were carried out on a total of seven filters, three in the far-ultraviolet (FUV; 1300–1800 Å) band and four in the near-ultraviolet (NUV; 2000–3000 Å) band. We carried out photometry of these observations that have a spatial resolution better than 1.″5. We present here the first results of this work, which is a matched catalog of 11,241 sources detected in three FUV and four NUV wavelengths. We make the catalog available online, which would be of use to the astronomical community to address a wide variety of astrophysical problems. We provide an expression to estimate the total count rate in the full point-spread function of UVIT that also incorporates the effect of saturation.

• Cost-effective and user-friendly 3D-printing approach for CE compact detection cells. • Flexible and reproducible producing of mini-C4D cells, measuring only 9.5×7.0×7.5 mm³. • On-capillary UV-PD cell with high sensitivity and minimal stray light. • Detection cells exhibit performance comparable to or surpassing existing counterparts. The growing demand for tailored detectors in capillary electrophoresis (CE), addressing tasks like field deployment or dual-detection analysis, emphasizes the necessity for compact detection cells. In this work, we propose cost-effective and user-friendly additive manufacturing (3D-printing) approaches to produce such miniaturized detection cells suitable for a range of CE applications. Firstly, capacitively-coupled contactless conductivity detection (C4D) cells of different sizes are fabricated by casting low-melting-point alloy into 3D-printed molds. Various designs of Faraday shields are integrated within the cells and compared. A mini-C4D cell (9.5×7.0×7.5 mm3) is produced, with limits of detection for alkaline cations ranging from 8-12 μM in a short–capillary based CE application. Secondly, ultraviolet photometric (UV-PD) detection cells are fabricated using 3D printing. These cells feature two narrow slits with a width of 60 μm, which are positioned along the path of incident and transmission light to facilitate collimation. A deep UV-LED (235 nm or 255 nm) is employed as the light source, and black resin is determined to be the optimal material for 3D printing the UV-PD cell, owing to its superior UV light absorption capabilities. The UV-PD cell is connected to the LED and photodetector through two optical fibers, making it easy to switch the light source and detector. The effective pathlength and stray light percentage for detecting on a 75 μm id capillary are 74 μm and 0.5 %, respectively. Thirdly, a dual-detection cell that combined C4D and UV-PD at a single detection point is proposed. The performance of direct detection by C4D and indirect detection by UV-PD is compared for detecting organic acids. The strategies for developing cost-effective compact detection cells facilitate the versatile integration of multiple detection methods in CE analysis. [ABSTRACT FROM AUTHOR]

Abstract Solar-blind deep-ultraviolet (DUV) photodetectors have attracted wide attention because of their extensive military and civil applications. The ternary oxide Zn 2 GeO 4 is an ideal material with a wide bandgap (E g = 4.69 eV). In this work, DUV photodetectors based on a ternary Zn 2 GeO 4 nanowire (NW) network were fabricated on SiO 2 /Si substrates. Reactive ion etching of the SiO 2 /Si wafer was used to grow the NW network to avoid contamination of the Au catalyst during synthesis of the Zn 2 GeO 4 NW network via high-temperature chemical vapor deposition. Photodetectors based the Zn 2 GeO 4 NW revealed fast response and recovery times, which is attributed to the unique cross-junction barrier-dominated conductance of the NW network. Results showed that the ternary oxide-based NW network is an ideal building block for nanoscale solar-blind photodetectors with superior performance. Highlights • A new method called reactive ion etching and apply it to a SiO 2 /Si wafer to produce a substrate on which to grow a Zn 2 GeO 4 NW network. • A high ratio (40,000 times) of light current to dark current and fast response and recovery times (within 600 and 250 ms, respectively). • The reason of outstanding responsibility was systemically investigated by adjusting the interim morphologies and interface of synthesized Zn 2 GeO 4 NW network. [ABSTRACT FROM AUTHOR]

The photodissociation of dichlorine monoxide (Cl2O) at 308, 248, and 193 nm was studied by photofragment translational energy spectroscopy. The primary channel upon excitation at 308 and 248 nm was Cl–O bond fission with production of ClO+Cl. A fraction of the ClO photoproducts also underwent spontaneous secondary dissociation at 248 nm. The center-of-mass translational energy distribution for the ClO+Cl channel at 248 nm appeared to be bimodal with a high energy component that was similar in shape to the 308 nm distribution and a second, low energy component with a maximum close to the threshold for the 2Cl+O(3P) channel. Observation of a bimodal distribution suggests that two pathways with different dissociation dynamics lead to ClO+Cl products. The high product internal energy of the second component raises the possibility that ClO is formed in a previously unobserved spin-excited state a 4Σ-. Following excitation at 193 nm, a concerted dissociation pathway leading to Cl2+O was observed in addition to primary Cl–O bond breakage. In both processes, most of the diatomic photofragments were formed with sufficient internal energy that they spontaneously dissociated. The time-of-flight distributions of the Cl2+O products suggest that these fragments are formed in two different channels Cl2(3Π)+O(3P) and Cl2(X 1Σ)+O(1D). [ABSTRACT FROM AUTHOR]

Ultraviolet two-photon photoselection, followed by visible one-photon absorption is applied to HCl to record the first double-resonant spin–orbit autoionization spectrum of a hydrogen halide, and the first rotationally resolved such spectrum of HCl. The J=2 level of the F 1Δ2(v=0) Rydberg state serves as the intermediate two-photon resonance. The ionization-detected absorption spectrum from this initial state, scanned across the 634 cm-1 interval between the lower 2Π3/2 and upper 2Π1/2 thresholds, shows a complex system consisting of hundreds of sharp lines converging to the accessible rotational limits of the upper spin–orbit threshold. The complexity of the spectrum is attributed to the relaxed selection rules associated with dipole transitions from a state in Hund’s case (a) to a manifold approaching Hund’s case (e), in concert with the irregularities expected for angular momentum coupling intermediate between the limits of case (c) and case (e). A simple case (e) fit over the central portion of the spectrum yields tentative assignment of a number of series converging to the J+=1/2, 3/2, and 5/2 levels of the ion. No evidence is found for series converging to higher rotational levels of the ion, even though such series are not excluded by angular momentum selection rules; transitions to Rydberg electronic angular momenta required for access to states of higher J+ are found associated with series observed converging to lower rotational thresholds. [ABSTRACT FROM AUTHOR]

Absolute photoabsorption cross sections for the lowest excited state (4 2Γ) of Kr2F and the ground state (1( 1/2 )u) of Kr+2 have been measured in the visible and ultraviolet (Kr2F: 248, 308, 335–600 nm; Kr+2 : 360–500 nm). As predicted by theory, the Kr2F spectrum is dominated by the 9 2Γ←4 2Γ band which peaks below 340 nm and correlates with the Kr+2 2( 1/2 )g ←1( 1/2 )u transition. However, Kr2F(4 2Γ) and Kr+2 (1( 1/2 )u) both absorb more strongly for wavelengths beyond ∼450 nm than expected, apparently owing to a nonthermalized Kr+2 vibrational distribution. Despite interference from Kr2F stimulated emission between ∼350 and 460 nm, the experimental results show the Kr2F(4 2Γ) and Kr+2 absorption profiles to be similar for λ≥460 nm but diverging rapidly as λ increases from 335 to 360 nm. At 360 nm, the absorption cross sections differ by a factor of 3. Contrary to theoretical expectations, the Kr2F absolute absorption cross section is consistently smaller (typically <40%) than that for Kr+2 which suggests that the impact of F- on the Kr+2 oscillator strengths is significant. [ABSTRACT FROM AUTHOR]

Herein, a comparative study focusing on the effects of measuring atmosphere on ultraviolet (UV) photodetection performance of ZnO nanostructures is presented. Various morphologies of ZnO nanostructures were synthesized by changing the hydrothermal temperature within 343–423 K. The ultraviolet photodetection performance of the samples was studied against dark ultraviolet light (360 nm, 800 μW/cm 2 ) under 200 sccm gas flows of argon and oxygen. The nanoflowers grown at 373 and 393 K showed the best photosensitivity and photoresponsivity under both argon and oxygen flows. Concerning the importance of active surface area, it was shown that the sample grown at 393 K serves higher accessible surface-to-volume ratio (qualitatively observable by SEM and confirmed by BET), higher concentration of freed electron due to oxygen vacancies (confirmed by PL) and consequently, the best UV photosensitivity. The comparative study between photodetection parameters in argon and oxygen atmospheres showed that although higher partial pressure of oxygen is favorable for all photodetection parameters like photosensitivity, photoresponsivity and decay time, it has adverse effects on rising time because rising time is directly coupled with the density of desorbed oxygen atoms. [ABSTRACT FROM AUTHOR]

Near-ultraviolet (NUV)-excitable phosphors composed of Ba 8.9-(1/2) p Na p Eu 0.1 Y 2 Si 6 O 24 ( p = 0–0.8) and Ba 8.7- q Na 0.4 Eu 0.1 Mn q Y 2 Si 6 O 24 ( q = 0–0.4) were prepared via a solid-state reaction in a reducing atmosphere. The X-ray diffraction patterns of the obtained phosphors were examined to index the peak positions. After Na + substitution for Ba 2+ in the Ba 8.9 Eu 0.1 Y 2 Si 6 O 24 host lattice, the clear shift from green to yellow emission was observed. The Gaussian components of Ba 8.9-(1/2) p Na p Eu 0.1 Y 2 Si 6 O 24 ( p = 0, 0.4, and 0.8) phosphors were exploited by using the three different Eu 2+ ion sites in the host lattice. The dependence of the luminescent intensity of the Mn 2+ co-doped ( q = 0–0.4) host lattices on the fixed Na + and Eu 2+ contents was also investigated. Co-doping Na + with Mn 2+ and Eu 2+ emitters in the host structure enabled efficient energy transfer from Eu 2+ to Mn 2+ . The mechanism underlying this energy transfer was also discussed. The Commission Internationale de I’Eclairage (CIE) coordinates near the yellow and red regions of the obtained phosphors were observed. Each of Ba 8.9 Eu 0.1 Y 2 Si 6 O 24 , Ba 8.7 Na 0.4 Eu 0.1 Y 2 Si 6 O 24 , and Ba 8.6 Na 0.4 Eu 0.1 Mn 0.1 Y 2 Si 6 O 24 phosphors with a 405 nm LED chip was fabricated. The color rendering index (CRI, R a ) at correlated color temperature (CCT) with the CIE coordinates was exhibited for the LEDs. The thermal quenching and activation energy for the Ba 8.7 Na 0.4 Eu 0.1 Y 2 Si 6 O 24 and Ba 8.6 Na 0.4 Eu 0.1 Mn 0.1 Y 2 Si 6 O 24 phosphors were measured. [ABSTRACT FROM AUTHOR]

The goal of this paper is to evaluate the accuracy of the commonly used ozone (O 3 ) instrument (the ultraviolet (UV) photometer) against a Federal Reference Method (Nitric Oxide –chemiluminescence) for ozone measurement in wildfire smoke plumes. We carried out simultaneous ozone measurement with two UV O 3 photometers and one nitric oxide–chemiluminescence (NO-CL) ozone detectors during wildfire season (Aug. 1–Sept. 30) in 2015 at the Mount Bachelor Observatory (MBO, 2763 m above mean sea level, Oregon, USA). The UV O 3 shows good agreement and excellent correlation to NO-CL O 3 , with linear regression slopes close to unity and R 2 of 0.92 for 1-h average data and R 2 of 0.93 for O 3 daily maximum 8-h average (MDA8). During this two-month period we identified 35 wildfire events. Ozone enhancements in those wildfire plumes measured by NO-CL O 3 and UV O 3 monitors also show good agreement and excellent linear correlation, with a slope and R 2 of 1.03 and 0.86 for O 3 enhancements (ΔO 3 ) and 1.00 and 0.98 for carbon monoxide (CO)-normalized ozone enhancement ratios (ΔO 3 /ΔCO), respectively. Overall, the UV O 3 was found to have a positive bias of 4.7 ± 2.8 ppbv compared to the NO-CL O 3 . The O 3 bias between NO-CL O 3 and UV O 3 is independent of wildfire plume tracers such as CO, particulate matter (PM 1 ), aerosol scattering, and ultrafine particles. The results demonstrate that the UV O 3 absorbance method is reliable, even in highly concentrated wildfire plumes. [ABSTRACT FROM AUTHOR]

Selective metal-AlGaN photodetectors based on the Schottky barrier and operating in UV spectral range have been developed. The selective photodiodes based on Ag-AlGaN Schottky barriers of different composition have been manufactured, which has made it possible to improve the photosensitivity in the UV spectral range and eliminate spurious signals in the long-wavelength part of the UV spectral range. This has made it possible to develop visible-blind photodetectors with the long-wavelength edge of photosensitivity lying at the wavelengths less than 350 nm. The width of the photosensitivity spectrum is within 15-40 nm, depending on the thickness of the Ag layer, which varies from 15 to 150 nm. The proper choice of the composition of the AlGaN solid solution ensures increase in the photoresponse and reduction of the FWHM spectrum width up to 11 nm by matching peaks of the Ag transmission spectrum and the absorption spectrum of the epitaxial layer. The sensitivity is 0.071 A/W. The combination of effects of wideband window and overthe- barrier transfer has made it possible to create the ultraselective UV photodetectors based on Au-AlGaN structures with a half-width of the photosensitivity spectrum of 5-6 nm for the wave range 350-375 nm and a sensitivity of up to 140 mA/W. Based on a structure with the upper AlGaN epitaxial layer (with the AlN content x = 0.1 or x = 0.06), selective photodetectors with the maximum photosensitivity at wavelengths of 355 nm and 362 nm have been developed. Application of an additional less wideband GaN layer has made it possible to independently control the short-wavelength and long-wavelength boundaries of the sensitivity range. [ABSTRACT FROM AUTHOR]

Aminotris(methylenephosphonic acid) is a commonly used reagent in circulating water to minimize deposit and corrosion inhibition that should be monitored. Aminotris(methylenephosphonic acid) was determined in circulating water using a photooxidation reaction to produce orthophosphate that was subsequently determined. The optimal conditions for analytical measurements were 1.0 g/L sodium persulfate oxidizing agent and a digestion time of 8 min. It was not necessary to control the pH. The optimum digestion efficiency of aminotris(methylenephosphonic acid) was 95% with good accuracy and precision and recoveries between 98% and 105%. The reported protocol is simple, rapid, and allows the on-line monitoring of aminotris(methylenephosphonic acid) in circulating water. [ABSTRACT FROM PUBLISHER]

We have developed a parallel code called the VoIgt profile Parameter Estimation Routine (VIPER) for automatically fitting the H I Lyα forest seen in the spectra of quasi-stellar objects (QSOs). We obtained the H I column density distribution function (CDDF) and linewidth (b) parameter distribution for z < 0.45 using spectra of 82 QSOs obtained using the Cosmic Origins Spectrograph and VIPER. The consistency of these with existing measurements in the literature validates our code. By comparing this CDDF with those obtained from hydrodynamical simulations, we constrain the H I photoionization rate (ΓH I) at z < 0.45 in four redshift bins. VIPER, together with the Code for Ionization and Temperature Evolution (CITE), which we developed for GADGET-2, allows us to explore parameter space and perform χ² minimization to obtain ΓH I. We notice that the b parameters from the simulations are smaller than those derived from observations. We show that the observed b parameter distribution and b versus log NH I scatter can be reproduced in simulations by introducing subgrid-scale turbulence. However, it has very little influence on the derived ΓH I. The ΓH I(z) obtained here, (3.9 ± 0.1) x 10-14 (1 + z)4.98 ± 0.11 s-1, is in good agreement with the values derived by us using flux-based statistics in a previous article. These values are consistent with the hydrogen ionizing ultraviolet (UV) background being dominated mainly by QSOs, without needing any contribution from non-standard sources of UV photons. [ABSTRACT FROM AUTHOR]

High pixel per inch and high-resolution micro-LED displays are attracting more and more attentions. The increasing pixel number requires a large amount of bonding pads and brings huge difficulties to micro-LED system design and lowers power efficiency as well. It is urgent to integrate row and column driving circuits onto the micro-LED panel. Here, we report a fully integrated active matrix programmable micro-LED system on panel (SoP) with ultraviolet and blue emission wavelengths. The micro-LED SoP has a resolution of 60 × 60 and pixel pitch of 70 μm. The micro-LED SoP was achieved by integrating micro-LED arrays with silicon-based p-channel metal-oxide semiconductor driving panel using fine-toned flip-chip bonding technology. With fully integrated scan and data circuits, the number of bonding pads was greatly reduced from 136 to 28, and large amount of metal interconnection lines were saved. The micro-LED SoP panel was mounted on a periphery driving board, and representative characters were displayed successfully. [ABSTRACT FROM AUTHOR]

Banded iron formations (BIFs) contain appreciable amounts of ferric iron (Fe 3+ ). The mechanism by which ferrous iron (Fe 2+ ) was oxidized into Fe 3+ in an atmosphere that was globally anoxic is highly debated. Of the three scenarios that have been proposed to explain BIF formation, photo-oxidation by UV photons is the only one that does not involve life (the other two are oxidation by O 2 produced by photosynthesis, and anoxygenic photosynthesis whereby Fe 2+ is directly used as electron donor in place of water). We experimentally investigated iron and oxygen isotope fractionation imparted by iron photo-oxidation at a pH of 7.3. The iron isotope fractionation between precipitated Fe 3+ -bearing lepidocrocite and dissolved Fe 2+ follows a Rayleigh distillation with an instantaneous 56 Fe/ 54 Fe fractionation factor of + 1.2 ‰ . Such enrichment in the heavy isotopes of iron is consistent with the values measured in BIFs. We also investigated the nature of the mass-fractionation law that governs iron isotope fractionation in the photo-oxidation experiments ( i.e. , the slope of the δ 56 Fe– δ 57 Fe relationship). The experimental run products follow a mass-dependent law corresponding to the high-T equilibrium limit. The fact that a ∼3.8 Gyr old BIF sample (IF-G) from Isua (Greenland) falls on the same fractionation line confirms that iron photo-oxidation in the surface layers of the oceans was a viable pathway to BIF formation in the Archean, when the atmosphere was largely transparent to UV photons. Our experiments allow us to estimate the quantum yield of the photo-oxidation process (∼0.07 iron atom oxidized per photon absorbed). This yield is used to model iron oxidation on early Mars. As the photo-oxidation proceeds, the aqueous medium becomes more acidic, which slows down the reaction by changing the speciation of iron to species that are less efficient at absorbing UV-photons. Iron photo-oxidation in centimeter to meter-deep water ponds would take months to years to complete. Oxidation by O 2 in acidic conditions would be slower. Iron photo-oxidation is thus likely responsible for the formation of jarosite–hematite deposits on Mars, provided that shallow standing water bodies could persist for extended periods of time. The oxygen isotopic composition of lepidocrocite precipitated from the photo-oxidation experiment was measured and it is related to the composition of water by mass-dependent fractionation. The precipitate-fluid 18 O/ 16 O isotope fractionation of ∼ + 6 ‰ is consistent with previous determinations of oxygen equilibrium fraction factors between iron oxyhydroxides and water. [ABSTRACT FROM AUTHOR]

We present the results of our UBV and JHKLM photometry for the semiregular pulsating variable V1027 Cyg, a supergiant with an infrared excess, over the period from 1997 to 2015 ( UBV) and in 2009-2015 ( JHKLM). Together with the new data, we analyze the photometric observations of V1027 Cyg that we have obtained and published previously. Our search for a periodicity in the UBV brightness variations has led to several periods from P = 212 to 320 in different time intervals. We have found the period P = 237 based on our infrared photometry. The variability amplitude, the lightcurve shape, and themagnitude of V1027 Cyg atmaximum light change noticeably from cycle to cycle. The deepest minimum was observed in 2011, when the amplitudes of brightness variations in the star reached the following values: Δ U = 128, Δ B = 110, Δ V = 105, Δ J = 030, Δ H = 035, Δ K = 032, Δ L = 026, and Δ M = 010. An ambiguous correlation of the B − V and U − B colors with the brightness has been revealed. For example, a noticeable bluing of the star was observed during the deep 1992, 2008, and 2011 minima, while the variations with smaller amplitudes show an increase in B − V at the photometric minima. The spectral energy distribution for V1027 Cyg from our photometry in the range 0.36 ( U)-5.0 ( M) μm corresponds to spectral types from G8I to K3I at different phases of the pulsation cycle. Low-resolution spectra of V1027 Cyg in the range λ4400-9200 ˚A were taken during 16 nights over the period 1995-2015. At the 1995 and 2011 photometric minima the star's spectrum exhibited molecular TiO bands whose intensity corresponded to spectral types M0-M1, while the photometric data point to a considerably earlier spectral type. We hypothesize that the TiO bands are formed in the upper layers of the extended stellar atmosphere. We have measured the equivalent widths of the strongest absorption lines, in particular, the infrared Ca II triplet in the spectrum of V1027 Cyg. The calcium triplet (Ca T) with W (Ca T) = 20.3 ± 1.8 ˚A as a luminosity indicator for supergiants places V1027 Cyg in the region of the brightest G-K supergiants. V1027 Cyg has been identified with the infrared source IRAS 20004+2955 and is currently believed to be a candidate for post-AGB stars. The evolutionary status of the star and its difference from other post-AGB objects are discussed. [ABSTRACT FROM AUTHOR]

Three dimensional diamond ultraviolet (UV) photodetector have been fabricated on diamond epitaxial layer through down-top approach, where diamond epitaxial layer was grown between metal electrodes. A thin diamond epitaxial layer was first grown on high-pressure high-temperature single crystal diamond substrate. Then, the diamond epitaxial layer was covered by interdigitated tungsten electrodes. Furthermore, another diamond epitaxial layer was grown on uncovered area. At last, UV-Ozone treatment was used to oxidize the surface. The optoelectronic performance of the photodetector was characterized, exhibiting a large responsivity and a repeatable transient response behavior. Moreover, down-top process is beneficial for the electrode conductivity stability. Also, an ohmic contact could be formed between tungsten and diamond during growth. The results indicate that down-top process is an efficient way for fabrication of three dimensional diamond photodetectors. [ABSTRACT FROM AUTHOR]

We compare common star formation rate (SFR) indicators in the local Universe in the Galaxy and Mass Assembly (GAMA) equatorial fields (~160 deg²), using ultraviolet (UV) photometry from GALEX, far-infrared and sub-millimetre (sub-mm) photometry from Herschel Astrophysical Terahertz Large Area Survey, and Hα spectroscopy from the GAMA survey. With a high-quality sample of 745 galaxies (median redshift = 0.08), we consider three SFR tracers: UV luminosity corrected for dust attenuation using the UV spectral slope β (SFRUV, corr), Hα line luminosity corrected for dust using the Balmer decrement (BD) (SFRHα, corr), and the combination of UV and infrared (IR) emission (SFRUV + IR). We demonstrate that SFRUV, corr can be reconciled with the other two tracers after applying attenuation corrections by calibrating Infrared excess (IRX; i.e. the IR to UV luminosity ratio) and attenuation in the Hα (derived from BD) against β. However, β, on its own, is very unlikely to be a reliable attenuation indicator. We find that attenuation correction factors depend on parameters such as stellar mass (M*), z and dust temperature (Tdust), but not on Hα equivalent width or SÂ'ersic index. Due to the large scatter in the IRX versus β correlation, when compared to SFRUV + IR, the β-corrected SFRUV, corr exhibits systematic deviations as a function of IRX, BD and Tdust. [ABSTRACT FROM AUTHOR]

Graphene holds great promise for novel optoelectronic devices due its exceptional optical properties. Here we report an anomalous photoresponse due to resonant excitonic effects in oxygen functionalized epitaxial graphene (EG) with gain exceeding 10 4 in the deep-ultraviolet (DUV) region. The method used to introduce the oxygen adatoms is via mild oxygen plasma treatment. Upon oxygen adsorption, spectral weight transfer occurs and a photoresponse emerges. The photoresponse in the oxygen plasma treated EG (OPTEG) is attributed to the enhancement of the resonant exciton in the DUV and suppression of optical conductivity below it, as evidenced in our spectroscopic ellipsometry measurements. Our result shows that the OPTEG produces large photoconductive gain, high selectivity, and detectivity in excess of 10 12 Jones in the DUV spectral range and can be harnessed to fabricate tunable graphene-based high-gain DUV photodetectors. [ABSTRACT FROM AUTHOR]

Characterization of the cysteine content of proteins is a key aspect of proteomics. By defining both the total number of cysteines and their bound/unbound state, the number of candidate proteins considered in database searches is significantly constrained. Herein we present a methodology that utilizes 266 nm UVPD to count the number of free and bound cysteines in intact proteins. In order to attain this goal, proteins were derivatized with N-(phenylseleno)phthalimide (NPSP) to install a selectively cleavable Se-S bond upon 266 UVPD. The number of Se-S bonds cleaved upon UVPD, a process that releases SePh moieties, corresponds to the number of cysteine residues per protein. [ABSTRACT FROM AUTHOR]

Highly oriented (201) Er3+-doped β-Ga2O3 (Er:Ga2O3) thin films with different doping concentrations were grown on (0001) sapphire substrates using radiofrequency magnetron sputtering. The crystal structure, optical absorption, near-infrared luminescence, and ultraviolet photoresponse properties of Er:Ga2O3 films were systematically studied. The evolution of lattice and energy band gap with increasing doping level confirms the chemical substitution of Er3+ ions into the Ga2O3 crystal lattice. The down-shifting near-infrared luminescence (∼1538 nm: ascribed to Er3+: 4I13/2-4I15/2) was observed under ultraviolet excitation. Moreover, an obvious deep ultraviolet photoresponse was also obtained in the formed thin films. [ABSTRACT FROM AUTHOR]

We present the analysis of multiband time series data for a sample of 24 Cepheids in the field of the Large Magellanic Cloud cluster NGC 1866. Very accurate BVI Very Large Telescope photometry is combined with archival UBVI data, covering a large temporal window, to obtain precise mean magnitudes and periods with typical errors of 1-2 per cent and of 1 ppm, respectively. These results represent the first accurate and homogeneous data set for a substantial sample of Cepheid variables belonging to a cluster and hence sharing common distance, age and original chemical composition. Comparisons of the resulting multiband period-luminosity and Wesenheit relations to both empirical and theoretical results for the Large Magellanic Cloud are presented and discussed to derive the distance of the cluster and to constrain the mass-luminosity relation of the Cepheids. The adopted theoretical scenario is also tested by comparison with independent calibrations of the Cepheid Wesenheit zero-point based on trigonometric parallaxes and Baade-Wesselink techniques. Our analysis suggests that a mild overshooting and/or a moderate mass-loss can affect intermediate-mass stellar evolution in this cluster and gives a distance modulus of 18.50 ± 0.01 mag. The obtained V,I colour-magnitude diagram is also analysed and compared with both synthetic models and theoretical isochrones for a range of ages and metallicities and for different efficiencies of core overshooting. As a result, we find that the age of NGC 1866 is about 140 Myr, assuming Z = 0.008 and the mild efficiency of overshooting suggested by the comparison with the pulsation models. [ABSTRACT FROM AUTHOR]

Extreme deconvolution (XD) of broad-band photometric data can both separate stars from quasars and generate probability density functions for quasar redshifts, while incorporating flux uncertainties and missing data. Mid-infrared photometric colours are now widely used to identify hot dust intrinsic to quasars, and the release of all-sky WISE data has led to a dramatic increase in the number of IR-selected quasars. Using forced photometry on public WISE data at the locations of Sloan Digital Sky Survey (SDSS) point sources, we incorporate this all-sky data into the training of the XDQSOz models originally developed to select quasars from optical photometry. The combination of WISE and SDSS information is far more powerful than SDSS alone, particularly at z > 2. The use of SDSS+WISE photometry is comparable to the use of SDSS+ultraviolet+near-IR data. We release a new public catalogue of 5537 436 (total; 3874 639 weighted by probability) potential quasars with probability PQSO > 0.2. The catalogue includes redshift probabilities for all objects. We also release an updated version of the publicly available set of codes to calculate quasar and redshift probabilities for various combinations of data. Finally, we demonstrate that this method of selecting quasars using WISE data is both more complete and efficient than simple WISE colour-cuts, especially at high redshift. Our fits verify that above z ~ 3 WISE colours become bluer than the standard cuts applied to select quasars. Currently, the analysis is limited to quasars with optical counterparts, and thus cannot be used to find highly obscured quasars that WISE colour-cuts identify in significant numbers. [ABSTRACT FROM AUTHOR]

The photodegradation of the ultraviolet (UV) filter octyl methoxycinnamate (OMC) is investigated in both dilute solution and in aggregated form. In dilute solution, the ratio of trans and cis isomers achieved at the photostationary state is solvent-dependent because of variations in the isomerization quantum yield. The two isomeric forms at the photostationary state are highly resistant to further photodegradation and no other UVA-absorbing species are formed. Aggregation of OMC, either in a neat film or in aqueous colloidal suspensions, leads to irreversible photodegradation of the molecule and the formation of multiple photoproducts. In addition to previously identified photoproducts like the UVB-absorbing cis and trans isomers and photodimers, we find photoproduct species whose absorption extends into the UVA. Characterization of the photophysical properties of these species indicates that they have long-lived excited-states (τf ＞ 1 ns, 400 nm), unlike the isomeric forms of OMC (τf ＜ 30 ps, 266 nm), and that excitation at 405 nm can sensitize the formation of singlet oxygen. These results show that the environment of OMC affects the photochemistry of the molecule and that the environmental conditions must be taken into account when considering the molecule's stability. In particular, aggregation of OMC molecules results in complex photochemistry that can produce species whose absorption extends into UVA and are capable of generating reactive oxygen species. [ABSTRACT FROM AUTHOR]

Thecooling of ionic species in the gas phase greatly simplifiesthe UV spectrum, which is of special importance when studying theelectronic and geometric structures of large systems, such as biorelatedmolecules and host–guest complexes. Many efforts have beendevoted to achieving ion cooling with a cold, quadrupole Paul iontrap (QIT), but one problem was the insufficient cooling of ions (upto ∼30 K) in the QIT. In this study, we construct a mass spectrometerfor the ultraviolet photodissociation (UVPD) spectroscopy of gas-phasecold ions. The instrument consists of an electrospray ion source,a QIT cooled with a He cryostat, and a time-of-flight mass spectrometer.With great care given to the cooling condition, we can achieve ∼10K for the vibrational temperature of ions in the QIT, which is estimatedfrom UVPD spectra of the benzo-18-crown-6 (B18C6) complex with a potassiumion, K+·B18C6. Using this setup, we measure a UVPDspectrum of cold calix[4]arene (C4A) complex with potassium ion, K+·C4A. The spectrum shows a very weak band and a strongone at 36018 and 36156 cm–1, respectively, accompaniedby many sharp vibronic bands in the 36000–36600 cm–1region. In the geometry optimization of the K+·C4Acomplex, we obtain three stable isomers: one endo and two exo forms.On the basis of the total energy and UV spectral patterns predictedby density functional theory calculations, we attribute the structureof the K+·C4A complex to the endo isomer (C2symmetry), in which the K+ionis located inside the cup of C4A. The vibronic bands of K+·C4A at 36 018 and 36 156 cm–1are assigned to the S1(A)–S0(A) andS2(B)–S0(A) transitions of the endo isomer,respectively. [ABSTRACT FROM AUTHOR]

In this work, the supramolecules (riboflavin and melamine) were used as a template for the self-assemble of ZnO nanostructures by adding into the growth solutions. After that, the composite nanostructures of nanoflowers-like p-type NiO/n-type ZnO nanosheets were grown following a two-step on the fluorine doped tin oxide substrate by the hydrothermal method. The riboflavin and melamine have a role in UV emission. Taking these advantages into account, the current–voltage (I–V) characterization of the ZnO/NiO heterojunction was performed at room temperature and showed an obvious nonlinear and rectifying response. Strong UV absorption with fast switching was observed from the ZnO/NiO composite heterojunction. The proposed UV photodetector based on this nanocomposite is more stable, possesses fast rising and decaying time response of approximately 100 ms. Further, a low leakage current was observed for the presented device. The findings in the present study indicates that the controlled nanostructures morphology is important to develop the efficient nanodevices for various applications. [ABSTRACT FROM AUTHOR]

The Galaxy Evolution Explorer ( GALEX) detected ultraviolet emission in about 50 % of multi-spin early-type galaxies (ETGs), suggesting the occurrence of a recent rejuvenation episode connected to the formation of these kinematical features. With the aim at investigating the complex evolutionary scenario leading to the formation of counter rotating ETGs (CR-ETGs) we use our Smooth Particle Hydrodynamic (SPH) code with chemo-photometric implementation. We discuss here the UV evolutionary path of two CR-ETGs, NGC 3593 and NGC 5173, concurrently best fitting their global observed properties, i.e., morphology, dynamics, as well as their total B-band absolute magnitude and spectral energy distribution (SED) extended over three orders of magnitude in wavelength. These simulations correspond to our predictions about the target evolution which we follow in the color-magnitude diagram (CMD), near-UV (NUV) versus r-band absolute magnitude, as a powerful diagnostic tool to emphasize rejuvenation episodes. [ABSTRACT FROM AUTHOR]