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Second-order-derivative plus fourth-order-derivative gravity is the ultraviolet completion of second-order-derivative quantum Einstein gravity. While it achieves renormalizability through states of negative Dirac norm, the unitarity violation that this would entail can be postponed to Planck energies. As we show in this paper, the theory has a different problem, one that occurs at all energy scales, namely that the Dirac norm of the vacuum of the theory is not finite. To establish this, we present a procedure for determining the norm of the vacuum in any quantum field theory. With the Dirac norm of the vacuum of the second-order-derivative plus fourth-order-derivative theory not being finite, the Feynman rules that are used to establish renormalizability are not valid, as is the assumption that the theory can be used as an effective theory at energies well below the Planck scale. This lack of finiteness is also manifested in the fact that the Lorentzian path integral for the theory is divergent. Because the vacuum Dirac norm is not finite, the Hamiltonian of the theory is not Hermitian. However, it turns out to be P T symmetric. When one continues the theory into the complex plane and uses the P T symmetry inner product, viz. the overlap of the left-eigenstate of the Hamiltonian with its right-eigenstate, one then finds that for the vacuum this norm is both finite and positive, the Feynman rules now are valid, the Lorentzian path integral now is well behaved, and the theory now can serve as a low energy effective theory, one that we show to have a real classical gravity limit. Consequently, the theory can now be offered as a fully consistent, unitary and renormalizable theory of quantum gravity. [ABSTRACT FROM AUTHOR]

The ultrafast electronic dynamics of pyrazine (C4N2H4) were studied by time-resolved photoelectron imaging (TRPEI) using the third (3ω, 4.7 eV) and fifth harmonics (5ω, 7.8 eV) of a femtosecond Ti:sapphire laser (ω). Although the photoionization signals due to the 5ω - 3ω and 3ω - 5ω pulse sequences overlapped near the time origin, we have successfully extracted their individual TRPEI signals using least squares fitting of the observed electron kinetic energy distributions. When the 5ω pulses preceded the 3ω pulses, the 5ω pulses predominantly excited the S4 (ππ*, ¹B1u+¹B2u) state. The photoionization signal from the S4 state generated by the time-delayed 3ω pulses was dominated by the D3(²B2g) ω S4 photoionization process and exhibited a broad electron kinetic energy distribution, which rapidly downshifted in energy within 100 fs. Also observed were the photoionization signals for the 3s, 3pz, and 3py members of the Rydberg series converging to D0(²Ag). The Rydberg signals appeared immediately within our instrumental time resolution of 27 fs, indicating that these states are directly photoexcited from the ground state or populated from S4 within 27 fs. The 3s, 3pz, and 3py states exhibited single exponential decay with lifetimes of 94 ± 2, 89 ± 2, and 58 ± 1 fs, respectively. With the reverse pulse sequence of 3ω - 5ω, the ultrafast internal conversion (IC) from S2(ππ*) to S1(nπ*) was observed. The decay associated spectrum of S2 exhibited multiple bands ascribed to D0, D1, and D3, in agreement with the 3ω-pump and 6ω-probe experiment described in our preceding paper [T. Horio et al., J. Chem. Phys. 145, 044306 (2016)]. The electron kinetic energy and angular distributions from S1 populated by IC from S2 are also discussed. [ABSTRACT FROM AUTHOR]

Metamaterials and periodic structures operating under high-power excitations are susceptible to breakdown. It was recently demonstrated that a localized breakdown created in a given region of a periodic structure can facilitate breakdown in other regions of the structure where the intensity of the incident electromagnetic fields may not be high enough to cause breakdown under normal circumstances. It was also demonstrated that this phenomenon is due to the generation of vacuum ultraviolet radiation at the location of the initial discharge, which propagates to the neighboring regions (e.g., other unit cells in a periodic structure) and facilitates the generation of a discharge at a lower incident power level. In this paper, we present the results of an experimental study conducted to determine the effective range of this physical phenomenon for periodic structures that operate in air and in pure nitrogen gas at atmospheric pressure levels. It is demonstrated that when breakdown is induced in a periodic structure using a high-power pulse with a frequency of 9.382 GHz, duration of 0.8 is, and peak power level of 25 kW, this phenomenon is highly likely to happen in radii of approximately 16-17 mm from the location of the initial discharge under these test conditions. The results of this study are significant in designing metamaterials and periodic structures for high-power microwave applications as they suggest that a localized discharge created in such a periodic structure with a periodicity less than 16-17 mm can spread over a large surface and result in a distributed discharge. [ABSTRACT FROM AUTHOR]

The first stages of planet formation usually occur when the host star is still in a (relatively) dense star-forming region, where the effects of the external environment may be important for understanding the outcome of the planet formation process. In particular, star-forming regions that contain massive stars have strong far-ultraviolet (FUV) and extreme ultraviolet (EUV) radiation fields, which can induce mass-loss from protoplanetary discs due to photoevaporation. In this paper, we present a parameter-space study of the expected FUV and EUV fields in N -body simulations of star-forming regions with a range of initial conditions. We then use recently published models to determine the mass-loss due to photoevaporation from protoplanetary discs. In particular, we focus on the effects of changing the initial degree of spatial structure and initial virial ratio in the star-forming regions, as well as the initial stellar density. We find that the FUV fields in star-forming regions are much higher than in the interstellar medium, even when the regions have stellar densities as low as in the Galactic field, due to the presence of intermediate-mass, and massive, stars (>5 M⊙). These strong radiation fields lead to the destruction of the gas component in protoplanetary discs within 1 Myr, implying that gas giant planets must either form extremely rapidly (<1 Myr), or that they exclusively form in star-forming regions like Taurus, which contain no intermediate-mass or massive stars. The latter scenario is in direct tension with meteoritic evidence from the Solar system that suggests the Sun and its protoplanetary disc was born in close proximity to massive stars. [ABSTRACT FROM AUTHOR]

The double photoionization of HI molecules has been investigated using vacuum ultraviolet synchrotron radiation in the energy range between 27 and 35 eV. The product ions have been detected by the use of time-of-flight mass spectrometry and the threshold energy for HI2+ and H++I+ formation has been determined. These results have been interpreted by the use of a theoretical model which has been previously applied by us to HBr2+ and HCl2+. On the basis of the reliability of such a model, an assessment of the systematic trends of the bond features along the HX2+ (X=F, Cl, Br, I) homologous series is given in this paper. In particular, the increase of the stability of these dications, in their lowest electronic states, when going towards the heavier molecules, has been rationalized considering the systematic variation of the charge transfer coupling between the H–X2+ and the H+–X+ states. [ABSTRACT FROM AUTHOR]

Photoabsorption measurements of NO bands have been made by vacuum-ultraviolet Fourier transform spectrometry with a resolution of 0.12 cm-1 in the wavelength region of 166.2–196.2 nm. Accurate line positions are obtained for the δ(υ,0) bands with υ=2, 3, the ε(υ,0) bands with υ=2, 3, and the β(υ,0) bands with υ=10,12,14. Absolute term values are found for the corresponding upper levels C(2,3), D(2,3), and B(10,12,14). Accurate rotational line integrated cross sections have also been obtained for the lines in these bands. Integrated cross sections reported in our earlier papers [J. Chem. Phys. 109, 1751 (1998); 112, 2251 (2000); 115, 3719 (2001); 116, 155 (2002); 117, 10621 (2002); 119, 8373 (2003)] have been revised, and the results reported here comprise the δ(υ,0) bands with υ=0–3, the ε(υ,0) bands with υ=0–3, the β(υ,0) bands with υ=6,7,9–12,14, and the γ(3,0) band. For each band, the band oscillator strength is obtained from the sum of the line strengths of all rotational lines, and these are compared with other published values. [ABSTRACT FROM AUTHOR]

In synchrotron radiation and electron storage rings, photon-stimulated gas desorption is a major contributor to gas load, leading to vacuum degradation and compromising the stability and quality of the beamline. Therefore, it is imperative to investigate the underlying mechanisms of photon-stimulated gas desorption to enhance the reliability of the experiments. In this paper, a theoretical model for analyzing the process of photon-stimulated desorption is presented, and the equations are solved numerically by considering the evacuation, bulk diffusion, thermal outgassing, adsorption, and desorption of surface gas molecules. The modified model can predict the yield of H 2 gas desorption induced by photon stimulation when synchrotron radiation is directed vertically onto various sample surfaces, utilizing the coupled multi-physics solution. The calculated results are consistent with the experimental measurements obtained from the Shanghai Synchrotron Radiation Facility. The results show that the photodesorption yield is related to the amount of surface-adsorbed molecules, which explains the observed decrease in the photodesorption yield with increasing accumulated photon dose. Furthermore, the study provides a theoretical approach to predicting the pressure evolution of photon-stimulated desorption. • A theoretical model for the analysis of photon-stimulated desorption (PSD) process is presented. • Reveals the mechanism underlying the decrease in the PSD yield with increasing accumulated photon dose. • Methods for predicting the evolution of pressure in the vacuum chamber before and after synchrotron radiation. • Methods for reducing the error between the tested PSD yield and the intrinsic PSD yield. [ABSTRACT FROM AUTHOR]

Highlights • SnTe as capping layer coatings in the vacuum and extreme ultraviolet spectral regions. • Design and fabrication of VUV quarter wave plates (QWP) based on SnTe/Al bilayer. • Extreme ultraviolet (EUV) improved facility for ellipsometric measurements. • Studying the polarimetric properties of SnTe/Al sample at the wavelength of (121.6 nm). • Angle-dependence phase retarder properties of SnTe/Al also reported in this study. Abstract Vacuum ultraviolet and extreme ultraviolet polarized light plays a significant role in many applications from materials science and solar physics investigations to optical components development. In this paper, we study the optical performances and the quarter wave retarder properties of aluminum coating capped with SnTe/Al thin film. The measurements have been performed by using a reflectometer properly improved for ellipsometric characterizations. The specimen has been fully characterized at hydrogen Lyman–alpha line (121.6 nm) by deriving the reflectance and the ellipsometric parameters, i.e. the ratio r and the phase difference δ. We found that the SnTe/Al bilayer behaves as phase retarder, although the performances differ from the ideal case. In fact, the polarimetric analysis combined with the optical test at different wavelengths allowed to identify carbon contamination on the top layer and a mild oxidation of the aluminum coating that affect the optical throughput. [ABSTRACT FROM AUTHOR]

An absorption has been detected at 1699.8 cm-1 in the midinfrared spectrum of the vacuum ultraviolet photolysis products of 1,3-butadiene (C4H6) trapped in Ar at 10 K, which on the basis of extensive13 C-substitution experiments is shown to belong to the C4 carbon chain. The behavior of the new band correlates closely with the ν2, C[larger_closed_square]C stretching vibration of linear C4 at 1543.4 cm-1 identified in an earlier paper. It is argued that the 1699.8 cm-1 absorption is a combination band involving the C[larger_closed_square]C stretching vibration and a bending mode of C4, with a cis-bent structure. [ABSTRACT FROM AUTHOR]

This paper describes a method for transferring a nanoscale pattern from a cyclic olefin polymer (COP) mold to the surface of UV curable polydimetylsiloxane (PDMS) on a glass substrate. The PDMS is first deposited on the patterned mold by spin-coating and photocuring. Vacuum ultraviolet (VUV) radiation is then used to activate the surface of both the PDMS and the glass substrate before bringing them into contact. Once a bond has been formed, the COP mold is peeled away, leaving the patterned PDMS on the glass substrate. Bonding tests were first carried out to determine the optimum VUV irradiation dose to form a permanent bond. The effectiveness of the proposed method was then demonstrated by transferring a periodic nanoscale pattern. Microscopic examination of the original and transferred patterns revealed that successful reproduction was achieved. A spectroscopic analysis was also performed to clarify the mechanism involved in the bonding process. The results suggested that VUV irradiation caused oxidation of the PDMS surface and the formation of OH groups. When the PDMS and the glass substrate were brought into contact, a dehydration reaction took place which caused the formation of siloxane ( O Si O ) bonds between the two materials. The proposed method offers the advantages of being simple and allowing deformation-free transfer of very fine patterns. It can also be applied to a wide range of nanoscale fabrication tasks. [ABSTRACT FROM AUTHOR]

The present paper is focused on the use of a vacuum ultraviolet absorption spectrometer (VUV) for gas chromatography (GC), within the context of flow modulated comprehensive two-dimensional gas chromatography (FM GC × GC). The features of the VUV detector were evaluated through the analysis of petrochemical and fatty acids samples. Besides responding in a predictable fashion via Beer’s law principles, the detector provides additional spectroscopic information for qualitative analysis. Virtually all chemical species absorb and have unique gas phase absorption features in the 120–240 nm wavelength range monitored. The VUV detector can acquire up to 90 full range absorption spectra per second, allowing its coupling with comprehensive two-dimensional gas chromatography. This recent form of detection can address specific limitations related to mass spectrometry ( e.g., identification of isobaric and isomeric species with very similar mass spectra or labile chemical compounds), and it is also able to deconvolute co-eluting peaks. Moreover, it is possible to exploit a pseudo-absolute quantitation of analytes based on pre-recorded absorption cross-sections for target analytes, without the need for traditional calibration. Using this and the other features of the detector, particular attention was devoted to the suitability of the FM GC × GC-VUV system toward qualitative and quantitative analysis of bio-diesel fuel and different kinds of fatty acids. Satisfactory results were obtained in terms of tailing factor (1.1), asymmetry factor (1.1), and similarity (average value 97%), for the FAMEs mixtures analysis. [ABSTRACT FROM AUTHOR]

There is growing theoretical and observational evidence that protoplanetary disc evolution may be significantly affected by the canonical levels of far-ultraviolet (FUV) radiation found in a star-forming environment, leading to substantial stripping of material from the disc outer edge even in the absence of nearby massive stars. In this paper, we perform the first full radiation hydrodynamic simulations of the flow from the outer rim of protoplanetary discs externally irradiated by such intermediate strength FUV fields, including direct modelling of the photon-dominated region which is required to accurately compute the thermal properties. We find excellent agreement between our models and the semi-analytic models of Facchini et al. (2016) for the profile of the flow itself, as well as the mass-loss rate and location of their 'critical radius'. This both validates their results (which differed significantly from prior semianalytic estimates) and our new numerical method, the latter of which can now be applied to elements of the problem that the semi-analytic approaches are incapable of modelling. We also obtain the composition of the flow, but given the simple geometry of our models we can only hint at some diagnostics for future observations of externally irradiated discs at this stage. We also discuss the potential for these models as benchmarks for future photochemical-dynamical codes. [ABSTRACT FROM AUTHOR]

Recently, a silicon-based ultrashallow-junction \p^+\- \n photodiode (B-layer diode) has been reported, with very high and very stable sensitivity in the vacuum-ultraviolet and extreme-ultraviolet spectral ranges. However, the ultrashallow nature of the junction leads to a high series resistance of the photodiode if no conductive capping layers are used. In a recent paper by Shi , a study on the relation between the sensitivity and the series resistance of the B-layer diodes, which can be large due to the shallow-junction depth, was presented. In this paper, an extensive analysis of the photodiode electrical and optical performance parameters and their interrelation is given. The influence of the series resistance on the response time of the photodiode for different illumination patterns is studied theoretically and also experimentally verified. It has been proven by modeling, simulations, and experiments that the time constant of the photodiode does not change significantly with the illumination spot area. This effect is due to temporary variations, going in opposite directions, of the equivalent series resistance, and the junction capacitance values found at the first instant a photogenerated charge are locally stored in the photodiode p-n junction. Also, the dependence of the degradation of the sensitivity on the incident wavelength and the diode vertical stack is examined through analysis and experimentation. [ABSTRACT FROM AUTHOR]

Free electron LASer in Hamburg is the first free electron laser user facility operating in the vacuum ultraviolet and soft X-ray wavelength range. Many user experiments require knowledge of the spatial and temporal coherence properties of the radiation. In this paper, we present a theoretical analysis of the coherence properties of the radiation for the fundamental and for the higher odd frequency harmonics. We show that temporal and spatial coherence reach their maxima close to the free electron laser (FEL) saturation but may degrade significantly in the post-saturation regime. We also find that the pointing stability of short FEL pulses is limited due to the fact that nonazimuthal FEL eigenmodes are not sufficiently suppressed. We discuss possible ways for improving the degree of transverse coherence and the pointing stability. [ABSTRACT FROM AUTHOR]

The luminescent properties of LSO:Ce (1 mol%) scintillators were characterized systematically under vacuum ultraviolet (VUV)–UV excitation. Under 185 nm VUV excitation, a broad emission band was detected in the wavelength range from 350 nm to 600 nm at different temperatures, which is ascribed to the 5d→4f electron transitions of Ce 3+ . Excitation wavelength and temperature effects on luminescent properties of LSO:Ce ceramic scintillators were investigated in this paper. At 50 K, the emission intensity of Ce1 (Ce 3+ locating in seven-oxygen-coordinated site) was much stronger than that of Ce2 (Ce 3+ locating in six-oxygen-coordinated site), and the total emission intensity excited by 355 nm (Ce1) was higher than that excited by 185 nm (host). The total luminescence intensity increases as the rising temperature in the temperature range of 150–300 K, which is originated from thermal enhancement of transportation of free carriers dominating Ce1 emission. [ABSTRACT FROM AUTHOR]

Flashover discharge occurs on spacecraft solar array with inverted potential gradient. The flashover discharges have been measured with an electron beam. However, it is difficult to charge the coupon surface uniformly. In this paper, ultraviolet light was used to achieve a uniform surface charging. The discharge current waveforms and surface potentials were measured with changing uniform surface potential. From these test results, the current waveform was calculated with a ladder circuit model. This model shows that the surface potential neutralization pattern is the same as that obtained with the experimental results. [ABSTRACT FROM PUBLISHER]

A high resolution vacuum ultraviolet (HRVUV) beamline based on a 6.65 m off-plane Eagle spectrometer is in operation at the Indus-1 synchrotron radiation source, RRCAT, Indore, India. To facilitate position sensitive detection and fast spectral recording, a new BaFBr:Eu 2+ phosphor based image plate (IP) detection system interchangeable with the existing photomultiplier (PMT) scanning system has been installed on this beamline. VUV photoabsorption studies on Xe, O 2 , N 2 O and SO 2 are carried out to evaluate the performance of the IP detection system. An FWHM of ~0.5 Å is achieved for the Xe atomic line at 1469.6 Å. Reproducibility of spectra is found to be within the experimental resolution. Compared to the PMT scanning system, the IP shows several advantages in terms of sensitivity, recording time and S / N ratio, which are highlighted in the paper. This is the first report of incorporation of an IP detection system in a VUV beamline using synchrotron radiation. Commissioning of the new detection system is expected to greatly enhance the utilization of the HRVUV beamline as a number of spectroscopic experiments which require fast recording times combined with a good signal to noise ratio are now feasible. [ABSTRACT FROM AUTHOR]

• First systematic experimental study of OME oxidation with different chain lengths. • Species pool is dominated by oxygenates and nearly independent of the chain length. • Highest oxygenated intermediate of OME 1-5 combustion is methyl formate. • Reactivity: shift of the intermediate's peak for longer OMEs to lower temperatures. • Significant fractions of ethanol detected using photoionization spectroscopy. This paper presents a systematic study of oxymethylene ethers (OMEs) oxidation in an atmospheric laminar flow reactor setup. Oxymethylene ethers with different number of oxymethylene ether groups (n = 0–5) have been investigated under lean and rich conditions (750–1250 K). The flow reactor is coupled to an electron ionization molecular-beam mass spectrometer (EI-MBMS) with high mass resolution to measure speciation data. Additional isomer-selective speciation analysis was performed using a novel atmospheric laminar flow reactor combined with double-imaging photoelectron photoion coincidence (i2PEPICO) spectroscopy at the vacuum ultraviolet radiation (VUV) beamline of the Swiss Light Source. The results show a dominance of oxygenated intermediates during the combustion of all OMEs in the investigated temperature regime. The observed species pool is thereby nearly independent of the OME's chain length. In particular the presence of significant fractions of ethanol is remarkable and indicates unknown or underestimated reaction pathways to form C–C bonds from OME structures. Formation of combustion intermediates during oxidation of longer OMEs occurs at lower temperatures and correlates with the ignition delay time. No hydrocarbons with more than four carbon atoms are detected. The combination of high mass resolution provided by EI-MBMS detection and isomer-selective analysis by i2PEPICO enables a complete overview of all intermediates. This allows for in-depth discussion and analysis of systematic trends for several intermediate species. [ABSTRACT FROM AUTHOR]

This paper presents an in-depth overview of the present status and novel developments in the field of plasma processing of low dielectric constant (low-k) materials developed for advanced interconnects in ULSI technology. The paper summarizes the major achievements accomplished during the last 10 years. It includes analysis of advanced experimental techniques that have been used, which are most appropriate for low-k patterning and resist strip, selection of chemistries, patterning strategies, masking materials, analytical techniques, and challenges appearing during the integration. Detailed discussions are devoted to the etch mechanisms of low-k materials and their degradation during the plasma processing. The problem of k-value degradation (plasma damage) is a key issue for the integration, and it is becoming more difficult and challenging as the dielectric constant of low-k materials scales down. Results obtained with new experimental methods, like the small gap technique and multi-beams systems with separated sources of ions, vacuum ultraviolet light, and radicals, are discussed in detail. The methods allowing reduction of plasma damage and restoration of dielectric properties of damaged low-k materials are also discussed. [ABSTRACT FROM AUTHOR]

ABSTRACT Photodissociation regions (PDRs) define the transition zone between an ionized and a dark molecular region. They consist of neutral gas which interacts with far-ultraviolet radiation and are characterized by strong infrared line emission. Various numerical codes treating one-dimensional PDRs have been developed in the past, simulating the complexity of chemical reactions occurring and providing a better understanding of the structure of a PDR. In this paper we present the three-dimensional code, 3d-pdr, which can treat PDRs of arbitrary density distribution. The code solves the chemistry and the thermal balance self-consistently within a given three-dimensional cloud. It calculates the total heating and cooling functions at any point in a given PDR by adopting an escape probability method. It uses a healpix-based ray tracing scheme to evaluate the attenuation of the far-ultraviolet radiation in the PDR and the propagation of the far-infrared/submm line emission out of the PDR. We present benchmarking results and apply 3d-pdr to (i) a uniform-density spherical cloud interacting with a plane-parallel external radiation field, (ii) a uniform-density spherical cloud interacting with a two-component external radiation field and (iii) a cometary globule interacting with a plane-parallel external radiation field. We find that the code is able to reproduce the benchmarking results of various other one-dimensional numerical codes treating PDRs. We also find that the accurate treatment of the radiation field in the fully three-dimensional treatment of PDRs can in some cases leads to different results when compared to a standard one-dimensional treatment. [ABSTRACT FROM AUTHOR]

Abstract: Gas phase photoabsorption studies of sulphur dioxide are carried out in the vacuum ultraviolet region using synchrotron radiation. Vibronic Analysis of the system lying in the region 1400–1600Å is reported for the first time. A larger number of spectral features are resolved compared to earlier reports. While most of the observed bands can be arranged into four series with successive band spacing of 500–620cm−1 in agreement with previous work, we observe two additional series with average separation of ∼1750 and ∼1000cm−1. Results of the ab initio calculations suggest that at least three dominant excitations are involved in the system viz. , and . The observed vibrational features are found to be mainly due to excitation of the combination modes (ν 1+ν 2) and (ν 2+ν 3) with some contributions from ν 1 and ν 3. Details of the experiment and analysis are discussed in this paper. [Copyright &y& Elsevier]

ISSIS imager has been thought as an open purpose instrument within the World Space Observatory (WSO) international space mission. The highest priorities of ISSIS, an instrument to be developed by Spain, are to guarantee high spatial resolution and high sensitivity down to the far ultraviolet (FUV). The paper displays the capacities of GOLD for multilayer deposition and FUV reflectometry, among other metrologies, for ISSIS optical elements. Deposition of coatings for ISSIS-WSO will be carried out in a new UHV system with a 75-cm diameter deposition chamber. The purpose of the new laboratory is the deposition of coatings satisfying the constraints for FUV space optics. The first target coating to be developed in this new laboratory is Al protected with MgF, with optimum reflectance down to ∼120 nm. GOLD's existing reflectometer is able to characterize flat pieces both by transmittance and reflectance, and the latter from near-normal to grazing incidence, in the range from 12 to 200 nm. Other metrologies that will be available at GOLD for ISSIS's coatings and filters include optical thickness of filters to assure parfocality, filter wedge, and coating and filter scattering. [ABSTRACT FROM AUTHOR]

In this paper we present our system design and methodology for making absolute quantum efficiency (QE) measurements through the vacuum ultraviolet (VUV) and verify the system with delta-doped silicon CCDs. Delta-doped detectors provide an excellent platform to validate measurements through the VUV due to their enhanced UV response. The requirements for measuring QE through the VUV are more strenuous than measurements in the near UV and necessitate, among other things, the use of a vacuum monochromator, good dewar chamber vacuum to prevent on-chip condensation, and more stringent handling requirements. [ABSTRACT FROM AUTHOR]

The effects of pH value, VUV intensity, initial dye concentration, initial H2O2 concentration, and TiO2 loading dose on the degradation of three azo dyes: acid Orange 8, acid Blue 29, and acid Blue 113 were studied to explore and compare the treatment efficiencies among the adopted AOPs. It was found that pH played an important role in the degradation of dyes using VUV irradiation. For VUV/H2O2, VUV/TiO2, and VUV/TiO2/H2O2 processes, the decoloration rates of the three azo dyes were more efficient under acidic conditions relative to alkaline conditions. The degradation rates of dyes increased with increasing concentrations of H2O2, but reaction rates were retarded at high concentrations of H2O2 because the H2O2 compound acted as a scavenger of the hydroxyl radical. In this paper, three azo dyes were decomposed efficiently by VUV irradiation only demonstrating the effectiveness of VUV direct photolysis. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we demonstrate that vacuum ultraviolet (VUV) irradiation was effective to promote the wet etch resistance of perhydro-polysilazane-based inorganic spin-on-glass (PSZ-SOG) film inside the gap. The baking condition of VUV irradiation was chosen at 150°C in 0.2Pa before furnace curing process. Observed the densification characteristics of various trench sizes (aspect ratio (AR)=3.1–0.13), all densification coefficient (Deff ) of the samples with VUV irradiation were larger than 0.90. On the contrary, for the sample without VUV irradiation, a remarkable reduction of Deff values from 0.99 to 0.58 was found while the AR increasing from 0.13 to 3.1. The better densification characteristics of PSZ-SOG films were mainly contributed to the VUV photon. Compared with the reaction mechanisms during VUV irradiation and furnace curing, VUV photon is responsible for triggering the Si–N bond dissociation and accelerating the conversion rate of PSZ. Finally, the new reaction mechanism makes SOG films denser at STI region without additional thermal budget. [Copyright &y& Elsevier]

Abstract-In this paper, thick-film ceramic-sheet panel as a dielectric-barrier microdischarge-plasma source has been fabricated, and the behaviors of the positive column in the counterelectrode structure have been experimentally observed according to various electrode gaps from 200 to 500 μm. The minimum gap distance between the electrodes, which directly affects the generation of the positive column, was suggested based on the infrared (IR) emission characteristics from the microdischarge plasma. Considering the experimental observations, it is confirmed that the IR efficiency remarkably increases when an efficient positive column is produced at the electrode gaps over 400 μm. [ABSTRACT FROM AUTHOR]

This paper studies the near transform-limited high-resolution tunable far-ultraviolet light which is generated by narrow-band tunable light both theoretically and experimentally. It shows the theoretical work about conversion efficiency of sum-frequency, which is restricted by phase-matching angle, walk-off angle and phase distortion and so on, and sets experiment to check this work successfully. Also the origin of chirp of dye laser is analysed. [ABSTRACT FROM AUTHOR]

Abstract: FLASH, the free electron laser at DESY in Hamburg, is the first facility of its kind providing intense, femtosecond radiation pulses in the vacuum ultraviolet and soft X-ray range for user experiments. A broad science program has been started in summer 2005 with applications in atomic and molecular physics, cluster physics, the study of warm dense matter and surface dynamics, and diffraction imaging of small structures and biological samples with nanometer resolution. A selection of first experimental results is highlighted in this paper. [Copyright &y& Elsevier]

Most of the mass of the interstellar medium is in neutral phases that are heated by far-ultraviolet radiation from star forming regions. The gas, in turn, emits line radiation in the infrared and submillimeter that potentially has great diagnostic value. In this paper, we will review the physical processes (including heating, cooling, gas phase and grain surface chemistry) that give rise to this line emission and present diagnostic diagrams. We will also discuss several examples where models of neutral gas emission have been used to interpret line emission, including observations of H2O and O2 in molecular clouds and an example which points out the caution that must be used when applying the diagnostics to kiloparsec-sized regions in other galaxies. [ABSTRACT FROM AUTHOR]

Abstract: (Y0.99Bi0.01)BO3 phosphor was prepared and its luminescent properties were investigated using the synchrotron radiation instrument in this paper. Site-selective luminescence of Bi3+ in the YBO3 host was demonstrated by exciting/monitoring with different wavelengths at low temperature in this research. At the same time, the energy transfer between the centers of Bi3+ ions occupying different symmetric sites was observed. The excited energy levels of Bi3+ were identified through assigning the emission and excitation spectra. The paths and mechanism of energy transfer between the centers of Bi3+ occupying different symmetric sites were discussed finally. [Copyright &y& Elsevier]

Plasma-based technology is of great importance for a range of industrial applications. However, due to the complexity of gas-phase and surface chemical reactions, the underlying plasma chemistry is still poorly understood, leading to a growing demand for experimental setups on plasma diagnostics. In this paper, we report an apparatus that combines tunable synchrotron vacuum ultraviolet (VUV) photoionization with molecular-beam mass spectrometry for detecting ionic and neutral species formed in the processes of plasma discharge. The products including reactive intermediates such as enols can be identified unambiguously with the measurements of photoionization mass spectrometry (PIMS) and photoionization efficiency spectra. The tunable VUV PIMS has been proven as an ideal and sensitive tool for a comprehensive understanding of plasma chemistry. [ABSTRACT FROM AUTHOR]

Abstract: Phosphors play a key role in the performances of display and lighting systems, their quantum efficiency needs to be investigated and improved. That is particularly true in plasma display panels (PDP) because of vacuum ultra violet (VUV) nature of the excitation. It is well established now that a good phosphor for electronic or ultraviolet excitation, is not necessarily a good choice for excitation in VUV. In order to study the behaviour of phosphors, it is necessary to record excitation and absorption spectra and to know precisely the spectral repartition of the excitation source. In the VUV energy range, sodium salicylate is very often used as a reference because of its constant quantum efficiency. In this paper we analyse this quantum efficiency in the near VUV energy range (below 10eV) and its evolution over time. We show that it is far from being constant at these energies and that it decreases in a non-homogeneous manner over time. We also determined the quantum efficiency, in the VUV range, of several NBS standard phosphors and BaMgAl10O17:Eu2+. [Copyright &y& Elsevier]

This paper reviews recent experimental results concerning the use of modern excilamps (excimer lamps) in photoscience and photochemical technology. The special characteristics of these sources of incoherent vacuum-UV (VUV)/UV radiation are presented and their applications in water and air remediation are discussed. Special attention is paid to the VUV (172 nm)-initiated oxidation and mineralization of organic water and air contaminants. For example, the VUV-initiated production of carbon dioxide and carbon monoxide during 172 nm irradiation of several saturated volatile organic substrates in the gas phase (e. g. methanol, ethanol, 2-propanol, 1,4-dioxane, cyclohexane, and n-hexane) was quantitatively verified by gas chromatography. Depending on the nature of the gaseous substrate and on the flow rate through the excimer-flow-through photoreactor different CO2/CO ratios were obtained. [ABSTRACT FROM AUTHOR]

Abstract: This paper presented a new hybrid process of vacuum ultraviolet (VUV) and TiO2/UV for the decomposition of gaseous formaldehyde (HCHO) at a typical indoor concentration level. The performance was assessed by a preliminary technical and economic analysis. Concentration, flow velocity, relative humidity and light intensity were investigated as process variables. The synergistic or combination effect between VUV and TiO2/UV was attained by comparing the experimental conversions with the calculated ones based on the purifier-in-series efficiency model. The results showed that the proposed hybrid process can be technically feasible and economically attractive for the decomposition of gaseous HCHO. The outstanding merit of the hybrid process is the complementation of advantages of VUV and TiO2/UV. VUV improved the conversion of HCHO markedly on the basis of TiO2/UV. Ozone produced by VUV could be decomposed by TiO2/UV and its concentration was less than the maximum recommended by the WHO at the flow velocity of 0.75m/s or more. There was weak combination effect between VUV and TiO2/UV and the behavior was analyzed in terms of the actions of ozone. The hybrid process was more economical than the TiO2/UV process with a cost reduction of 60% for removing per kg HCHO. [Copyright &y& Elsevier]

The paper deals with the results of experimental investigation of spectrally averaged group reflectivities R(Δλ) in a vacuum ultraviolet (hν ∼ 10 to 70 eV) spectral range of commercial samples of high-temperature dielectric materials (α-Al2O3, SiO2, BNC) under conditions of a prethreshold (prior to the beginning of developed surface evaporation) power density of probing radiation. [ABSTRACT FROM AUTHOR]

Direct imaging of the magnetosphere by instruments on the IMAGE spacecraft is supplemented by simultaneous observations of the global aurora in three far ultraviolet (FUV) wavelength bands. The purpose of the multi-wavelength imaging is to study the global auroral particle and energy input from the magnetosphere into the atmosphere. This paper describes the method for quantitative interpretation of FUV measurements. The Wide-Band Imaging Camera (WIC) provides broad band ultraviolet images of the aurora with maximum spatial resolution by imaging the nitrogen lines and bands between 140 and 180 nm wavelength. The Spectrographic Imager (SI), a dual wavelength monochromatic instrument, images both Doppler-shifted Lyman-a emissions produced by precipitating protons, in the SI-12 channel and 01135.6 nm emissions in the SI-13 channel. From the SI-12 Doppler shifted Lyman-a images it is possible to obtain the precipitating proton flux provided assumptions are made regarding the mean energy of the protons. Knowledge of the proton (flux and energy) component allows the calculation of the contribution produced by protons in the WIC and SI-13 instruments. Comparison of the corrected WIC and SI-13 signals provides a measure of the electron mean energy, which can then be used to determine the electron energy flux. To accomplish this, reliable emission modeling and instrument calibrations are required. In-flight calibration using early-type stars was used to validate the pre-flight laboratory calibrations and determine long-term trends in sensitivity. In general, very reasonable agreement is found between in-situ measurements and remote quantitative determinations. [ABSTRACT FROM AUTHOR]

A novel high-frequency driving scheme was proposed in this paper to improve the luminous efficiency of a plasma display. High-frequency oscillating waveform was applied to the address electrodes of the conventional three-electrodes ac-type plasma display panel during the sustaining period. More vacuum ultraviolet rays were generated by the high-frequency waveform so that the luminance and luminous efficiency could be enhanced. From experiments on an 8.5-in panel, the luminance was improved and the luminous efficiency was enhanced more than 40%. [ABSTRACT FROM AUTHOR]

Thin films of MgF2 deposited by evaporation is a material widely used for its transparency in the far ultraviolet (FUV) down to ∼115 nm. In this paper the optical properties of ion-beam sputtered (IBS) MgF2 in the FUV are investigated and compared with MgF2 films deposited by evaporation. A slightly higher transparency at the 121.6-nm, H Lyman α line was obtained for IBS MgF2 films compared to films deposited by evaporation, which makes IBS MgF2 a promising protective material for Al reflective coatings. Experimental work on Al films that were protected with a thin evaporated MgF2 film followed by an IBS MgF2 film to produce a protective coating with optimum thickness showed a reflectance at 121.6 nm that was higher by about 3% compared to an Al film protected with an all-evaporated MgF2 film. [Copyright &y& Elsevier]

Photostability of polymers is an important issue since most polymers tend to loose their original properties upon exposure to light, especially to ultraviolet radiation. Polycarbonates are widely used industrial materials because of their excellent properties, which includes transparency, high tensile strength, impact resistance and rigidity. In this paper, we present results on 172 nm photodegradation of polycarbonate (PC) films. PC films of 50 μm thickness were irradiated for up to 20 min using a Xe2&ast; excimer lamp system. Ex situ UV visible spectroscopic investigation of the treated films revealed the appearance of two strong absorption bands at 279 and 317 nm and a third broad band centred around 380 nm whose intensity increased linearly with illumination time. The morphological changes were characterised by atomic force microscopy and resulted in a gradually increasing roughness, being a linear function of irradiation time. The interpretation of the observed chemical degradation is based on attenuated total reflection IR and X-ray photoelectron spectroscopic measurements which show cleavage of the aromatic C–C and carboxylic CO–O bonds together with some nitrogen incorporation into the surface layer of the irradiated films. [Copyright &y& Elsevier]

This paper consists of a general presentation of the Storage Ring FEL activities at LURE (Orsay). We first summarize the results obtained previously with an optical klystron installed on the ACO storage ring, and then make a presentation of the different projects that have begun on the new storage ring Super-ACO. The ACO storage ring experiments were of two kinds: the Free Electron Laser oscillator (FEL), and the coherent harmonic generation (CHG). The first allowed us to reach the visible spectral range, between 6500 and 4600 Å. In the second, we were able to produce coherent emission in the VUV: it was the shortest wavelengths (1773 and 1064 Å) ever obtained with an optical klystron or an undulator acting as a nonlinear medium. In this last configuration, the fundamental wave was an external pulsed and doubled Nd-Yag laser, focused in the optical klystron. The new Super-ACO storage ring has been equipped with a new optical klystron. The first ‘‘spontaneous emission’’ spectra have been observed and they show that the performance is in good agreement with theoretical predictions. FEL oscillator experiments in the visible range are planned for the end of the year. In parallel, CHG experiments in the VUV will begin. [ABSTRACT FROM AUTHOR]

In this paper, the design, construction, and test procedure of a closing switch prototype based on thyristors is described. In particular, details are given about the design criteria and about the triggering board architecture, which is a high side biased, self supplied unit using the electrical energy derived from a local snubber network for the gate drive. The structure guarantees a hard firing gate pulse for the required high dI/dt application. Further, the results of the prototype tests are presented and discussed. The stack assembly has a holding voltage of 6.5 kV and is used for switching a series resonant circuit with a ringing frequency of 12 kHz for a pulsed inductive vacuum ultraviolet source. Maximum current amplitudes of 13 kA and pulse energies of more than 600 J were switched during the test procedure. [ABSTRACT FROM AUTHOR]

Advances in free electron lasers (FELs) which generate high energy photons are expected to open novel nonlinear optics in the x-ray and vacuum ultraviolet (VUV) regions. In this paper, we report a new method for performing VUV-FEL focusing experiments. A VUV-FEL was focused with Kirkpatrick-Baez optics on a multilayer target, which contains fused silica as a fluorescent material. By measuring the fluorescence, a 5.6×4.9 μm2 focal spot was observed in situ. Fluorescence was used to measure the saturable absorption of VUV pulses in the tin layer. The transmission increases nonlinearly higher with increasing laser intensity. [ABSTRACT FROM AUTHOR]

193 nm photoresist patterns printed by optical lithography are known to present significant linewidth roughness (LWR) after the lithographic step that is partially transferred into the underlayers during plasma etching processes. In this study, we identify the factors that impact the photoresist pattern sidewalls roughness during plasma exposure. Among them, plasma vacuum ultraviolet light (110–210 nm) is shown to be the main contributor to the LWR decrease induced by plasma etching processes. In this paper, we also demonstrate the strong correlation between LWR obtained after plasma exposure and the surface roughening mechanisms taking place on top of the resist patterns. [ABSTRACT FROM AUTHOR]

• Vacuum UV photoabsorption spectrum of trans-1,2-C 2 H 2 Cl 2 for the first time between 5.0 eV and 20.0 eV. • Analysis of electronic and vibrational Rydberg transitions. • Detailed analysis for the first time of the valence transitions. • Interpretation and assignments based on quantum chemical calculations. This paper investigates in detail the vacuum UV photoabsorption spectrum of trans-1,2-C 2 H 2 Cl 2 in the 5–20 eV range using synchrotron radiation. Quantum chemical calculations are applied to the electronic transitions. Particular attention has been paid to the 2a u (π)→2b g (π*) transition included in the broad band observed at 6.30 eV. The Rydberg 2a u (π)→R3s transition is presumably observed at 6.27 eV. Below 6.0 eV the structure(s) are assigned to π→σ* transition(s). The abundantly structured spectrum observed between 7.0 eV and 12.0 eV has been analyzed in terms of vibronic transitions to ns- (δ ¯ =0.844) and nd/4f- (δ ¯ =0.03/0.011) Rydberg states, converging to the 2a u −1 ionization continuum, to two series of np- (δ ¯ = 0.66 and 0.40) states converging to the 5a g −1 continuum, to ns- (δ ¯ =0.983) and nd- (δ ¯ = –0.06) states converging to the 4b u −1 continuum and to two np-type (δ ¯ = 0.51 and 0.26) series converging to the 1b g −1 continuum. These data are complemented by an analysis of the vibrational structure of the individual Rydberg states. Comparisons with previously reported values are provided. Several other spectral features Table S2 (see Supplementary Material) in the 12–20 eV range are tentatively assigned to transitions to Rydberg states converging to higher ionic excited states of trans-1,2-C 2 H 2 Cl 2. Assignments of the vibrational structure of some of these transitions are also proposed. [ABSTRACT FROM AUTHOR]

We proposed and demonstrated an optical dry etching method for transferring a pattern on a photomask to a surface of plastics by decomposing the irradiated area using the high energy of vacuum ultraviolet light (VUV) at room temperature and pressure. Two kinds of wavelengths of 160 nm and 172 nm were used as the vacuum ultraviolet light, and the patterning performances for polymethyl methacrylate (PMMA) and polycarbonate (PC) were compared. As a result, it was revealed that proportional relationships were obtained between the etching rate and the irradiation dose for both wavelengths, and the cross-sectional profiles were anisotropic. In addition, both PMMA and PC were etched at a wavelength of 160 nm, whereas PC could not be etched at a wavelength of 172 nm, suggesting that it correlates with the bond dissociation energies of the molecular bonds of the materials and the energies of the photons. Furthermore, by combining this method with the optical bonding method that we had previously developed to bond surfaces irradiated with VUV, we have demonstrated a method for fabricating microfluidic devices by irradiating only with VUV. This paper shows that this technique is a new microfabrication method suitable for simple and mass production of plastic materials. [ABSTRACT FROM AUTHOR]

Microplasma sources typically take advantage of pd (pressure  ×  size) scaling by increasing pressure to operate at dimensions as small as tens of microns. In many applications, low pressure operation is desirable, which makes miniaturization difficult. In this paper, the characteristics of low pressure microplasma sources excited by microwave power are discussed based on results from experimental and computational studies. The intended application is production of VUV radiation for chemical analysis, and so emphasis in this study is on the production of resonant excited states of rare gases and radiation transport. The systems of interest operate at a few to 10 Torr in Ar and He/Ar mixtures with cavity dimensions of hundreds of microns to 1 mm. Power deposition is a few watts which produces fractional ionization of about 0.1%. We found that production of VUV radiation from argon microplasmas at 104.8 nm and 106.7 nm saturates as a function of power deposition due to a quasi-equilibrium that is established between the electron temperature (that is not terribly sensitive to power deposition) and the population of the Ar(4s) manifold. [ABSTRACT FROM AUTHOR]

Low-pressure (a few to hundreds of millitorrs) inductively coupled plasmas (ICPs), as typically used in microelectronics fabrication, often produce vacuum-ultraviolet (VUV) photon fluxes onto surfaces comparable to or exceeding the magnitude of ion fluxes. These VUV photon fluxes are desirable in applications such as sterilization of medical equipment but are unwanted in many materials fabrication processes due to damage to the devices by the high-energy photons. Under specific conditions, VUV fluxes may stimulate etching or synergistically combine with ion fluxes to modify polymeric materials. In this regard, it is desirable to control the magnitude of VUV fluxes or the ratio of VUV fluxes to those of other reactive species, such as ions, or to discretely control the VUV spectrum. In this paper, we discuss results from a computational investigation of VUV fluxes from low-pressure ICPs sustained in rare gas mixtures. The control of VUV fluxes through the use of pressure, pulsed power, and gas mixture is discussed. We found that the ratio, β, of VUV photon to ion fluxes onto surfaces generally increases with increasing pressure. When using pulsed plasmas, the instantaneous value of β can vary by a factor of 4 or more during the pulse cycle due to the VUV flux more closely following the pulsed power. [ABSTRACT FROM AUTHOR]

Natural organic matter (NOM) present in surface water sources undergoes significant structural and chemical changes during the application of vacuum ultraviolet (VUV)-based advanced oxidation process (AOP), which leads to the formation of undesired by-products such as aldehydes. Partial NOM mineralization can occur depending on the fluence received. In this paper, the VUV-induced degradation of NOM and the subsequent formation of by-products were experimentally studied. Two natural waters (Trepanier Creek and Capilano Reservoir, in British Columbia, Canada) and two synthetic waters (Suwannee River, Southern Georgia and Northern Florida; Nordic Reservoir, Vallsjøen, Skarnes, Norway) were used. While the process started with partial oxidation of NOM, extensive irradiation (i.e., high fluence) led to complete mineralization of NOM. The rates of mineralization were greatly dependent on the nature of NOM and on the presence of inorganic compounds in the water matrix, such as carbonates and bicarbonates. A faster mineralization rate was obtained with waters containing NOM with a lower average molecular weight. Size exclusion chromatography analysis showed that high-molecular-weight (HMW) molecules were readily degraded, even from the beginning of the treatment. The fraction of low-molecular-weight (LMW) compounds also reduced, but at a slower rate, largely because LMW compounds were both formed through partial degradation of HMW compounds and degraded by hydroxyl radicals. The concentration of aldehydes and trihalomethane formation potentials increased up to 120-700 ppb, respectively, after receiving a fluences in the range of ), but decreased with relatively higher fluencies (). [ABSTRACT FROM AUTHOR]

Mono-filamentary dielectric barrier discharge (MF-DBD), occurring within 1 mm gap of atmospheric pressure pure nitrogen and operating with a sinusoidal electric supply at about 8 kHz, is studied in this paper. A thorough electrical analysis allows experimental determination of the ignition and extinction voltages, respectively (15 750 +- 50) V and (2097 +- 7) V, the injected energy (158 +- 2) J and charge (17.22 +- 0.22) nC in a single filament. The mean axial reduced electric field is equal to (644 +- 2) Td at ignition. An empirical technique is proposed to evaluate these discharge parameters by avoiding bulky calculations. Optical emission spectroscopic measurements of the vacuum ultraviolet (VUV), ultraviolet (UV), visible and near infrared (IR) emissions are presented and discussed. Two atomic nitrogen lines attributed to the decay of the N[2s2p23s 2P] triplet towards N[2s22p3 2Ddeg] level are observed at 150 and 175 nm, together with the Lyman-Birge-Hopfield system ({\rm N}_{2}[a\,{}^1\Pi_{\rm g} ]\to {\rm N}_2 [X\,{}^1\Sigma_{\rm g}^+ ]) in the VUV range. The second positive system (N2[C 3Pu] - N2[B 3Pg]) dominates the UV and visible-blue spectra. The (0-0) transition of the first negative system ({\rm N}_2^+ [B\,{}^2\Sigma_{\rm u}^+ ]\to {\rm N}_2^+ [X\,{}^2\Sigma_{\rm g}^+ ]) peaking at 391.4 nm, the first positive system ({\rm N}_{2}[B\,{}^3\Pi_{\rm g} ]\to {\rm N}_2 [A\,{}^3\Sigma_{\rm u}^+ ]) and the Herman IR transitions ({\rm N}_{2}[C''\,{}^5\Pi_{\rm u} ]\to {\rm N}_2 [A'\,{}^5\Sigma_{\rm g}^+ ]) are also present. Both our VUV and near IR spectra are consistent with recently reported results in hollow cathode and cylindrical DBDs. The electrical and spectroscopic experimental results reported here are useful for ongoing and forthcoming modelling of filamentary nitrogen dielectric barrier discharges. [ABSTRACT FROM AUTHOR]

Presents an abstract of a paper focusing on optical converters for circularly polarized vacuum ultraviolet and soft-x-ray radiation. Method by which optical devices convert linearly polarized radiation; Phase-shifter designs; Potential capabilities of optical insertion devices as an alternative tool to generate variably polarized synchrotron radiation.