Vacuum Ultraviolet Emission Spectra Research Articles

Line identification of boron and nitrogen emissions in extreme- and vacuum-ultraviolet wavelength ranges in the impurity powder dropping experiments of the Large Helical Device and its application to spectroscopic diagnostics

An impurity powder dropper was installed in the 21st campaign of the Large Helical Device experiment (Oct. 2019–Feb. 2020) under a collaboration between the National Institute for Fusion Science and the Princeton Plasma Physics Laboratory for the purposes of real-time wall conditioning and edge plasma control. In order to assess the effective injection of the impurity powders, spectroscopic diagnostics were applied to observe line emission from the injected impurity. Thus, extreme-ultraviolet (EUV) and vacuum-ultraviolet (VUV) emission spectra were analyzed to summarize observable impurity lines with B and BN powder injection. Emission lines released from B and N ions were identified in the EUV wavelength range of 5–300 Å measured using two grazing incidence flat-field EUV spectrometers and in the VUV wavelength range of 300–2400 Å measured using three normal incidence 20 cm VUV spectrometers. BI–BV and NIII–NVII emission lines were identified in the discharges with the B and BN powder injection, respectively. Useful B and N emission lines which have large intensities and are isolated from other lines were successfully identified as follows: BI (1825.89, 1826.40) Å (blended), BII 1362.46 Å, BIII (677.00, 677.14, 677.16) Å (blended), BIV 60.31 Å, BV 48.59 Å, NIII (989.79, 991.51, 991.58) Å (blended), NIV 765.15 Å, NV (209.27, 209.31) Å (blended), NVI 1896.80 Å, and NVII 24.78 Å. Applications of the line identifications to the advanced spectroscopic diagnostics were demonstrated, such as the vertical profile measurements for the BV and NVII lines using a space-resolved EUV spectrometer and the ion temperature measurement for the BII line using a normal incidence 3 m VUV spectrometer.

Study of VUV Emission From Xe–Ne Microhollow Cathode Discharge in the Self-Pulsing Regime

This article by employing a zero-dimensional model investigates vacuum ultraviolet (VUV) emission from a xenon–neon microdischarge. The effects of the pressure, the input voltage, and the neon fraction are carefully studied. For specific input voltages, the microdischarge operates in an oscillatory regime which is called the self-pulsing regime. The self-pulsing frequency is mainly affected by the input voltage as well as the pressure. Increasing the input voltage enhances the average densities but has no effects on the peak densities. However, the pressure has significant effects on both densities. The main peaks of the VUV emission spectrum are seen at $\lambda =173$ nm and $\lambda =147$ nm which are attributed to xenon triplet-excited dimers and resonance-level excited atoms, respectively. Adding the neon gas enhances the emission at 147 nm through reducing the power loss in elastic collisions, but attenuates the emission at 173 nm. The results also show that steady-state densities of the major VUV emitters in the stationary regime are higher than the time average densities in the self-pulsing regime. Although, the lower power consumption of the self-pulsing regime has a more decisive effect such that the VUV emission efficiency in the self-pulsing regime is greater than that of the stationary regime.

Photoluminescence spectrum study of defects of potassium dihydrogen phosphate crystals irradiated by different laser fluences

The laser-induced damage to potassium dihydrogen phosphate (KDP) crystal restricts the development of high power laser systems and attract the attention of researchers. The defects are essential for the understanding of the laser-induced damage to KDP crystals. The defects in KDP crystals are commonly related to <inline-formula><tex-math id="Z-20200908091635-1">\begin{document}$ \rm H_2PO_4^{-} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="17-20200482_Z-20200908091635-1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="17-20200482_Z-20200908091635-1.png"/></alternatives></inline-formula> groups. The defects of KDP crystal have been studied extensively, however the changes of defects of KDP crystal with low fluence and high fluence have not been investigated sufficiently. The synchrotron radiation technology is a sensitive method of detecting the defects. The vacuum ultraviolet photoluminescence (PL) emission spectra can provide microscopic structural changes in KDP crystals. In this work, we investigate the defects of KDP crystals irradiated with different fluences by vacuum ultraviolet PL emission spectra. The vacuum ultraviolet spectra are obtained at the 4B8 beam line in Beijing synchrotron radiation facilities. Each KDP crystal spectrum is measured from 200 to 400 nm and 400 to 800 nm. The emission spectra of KDP crystal irradiated with different fluences are fitted for illustration. Each Gaussian curve represents a kind of defect. Comparing the retired components with KDP crystal irradiated by 11.5 J/cm<sup>2</sup>, the new band at 231.55 nm emerges in the spectra of KDP crystal irradiated by 9.0 J/cm<sup>2</sup>. The intrinsic luminescence band is assigned to the radiative annihilation of self-trapped excitons. According to our previous work, the short chain structures mainly exist in the crystal irradiated by 9.0 J/cm<sup>2</sup>, and the long chain structure is mainly in the crystal irradiated by 11.5 J/cm<sup>2</sup>. The retired components have the short, medium and long chain. The length of P—O bond in the short chain is shorter than that in the long chain structure. The overlap between phosphorus 3<i>s</i> orbitals and oxygen 2<i>p</i> increases, and the radiative annihilation of STEs becomes stronger. So the band at 231.55 nm emerges in the spectrum of KDP crystal irradiated by 9.0 J/cm<sup>2</sup>. It suggests that the structure of the retired component and the structure of KDP crystal irradiated by 9.0 J/cm<sup>2</sup> are different. The results provide an insight into the defects in KDP crystals. It is meaningful to study the mechanism of laser-induced damage to KDP crystal.

Photoluminescence, scintillation properties and trap states of La2Si2O7Ce single crystal

Single crystal of La2Si2O7:Ce (LaPS:Ce) was successfully grown by floating zone method for the first time. The structure of as grown sample is confirmed to be monoclinic with space group P21/c by x-ray diffraction and energy dispersive spectra. Its photoluminescence (PL) and scintillation properties of LaPS:Ce crystal were characterized through vacuum ultra-violet excitation and emission spectra, PL decay curve, x-ray excitation luminescence spectrum, γ-ray multi-channel spectrum and afterglow spectrum. Emission peaks of this material are around 3.5 eV and 3.3 eV, corresponding to the typical transition 5d → 4f of Ce3+. The PL decay time of LaPS:Ce is 29.3 ns. The light yield of the sample is determined to be about 5400 ph MeV−1 with a low afterglow level. The trap states in LaPS:Ce are also studied through the thermally stimulated luminescence measurement.

Controlling the emission profile of an H2discharge lamp to simulate interstellar radiation fields

Context. Microwave discharge hydrogen-flow lamps have been used for more than half a century to simulate interstellar ultraviolet radiation fields in the laboratory. Recent discrepancies between identical measurements in different laboratories, as well as clear wavelength dependent results obtained in monochromatic (synchrotron) experiments, hint at a more elaborate dependence on the exact discharge settings than assumed so far.Aims. We have investigated systematically two lamp geometries in full dependence of a large number of different running conditions and the spectral emission patterns are characterized for the first time with fully calibrated absolute flux numbers.Methods. A sophisticated plasma lamp calibration set-up has been used to record the vacuum-ultraviolet emission spectra with a spectral resolution of 0.5 nm and bandwidth of 1.6 nm in the 116–220 nm region. Spectra are compared with the output of a calibrated D2 -lamp which allows a derivation of absolute radiance values.Results. The general findings of over 200 individual measurements are presented, illustrating how the lamp emission pattern depends on i) microwave power; ii) gas and gas mixing ratios; iii) discharge lamp geometry; iv) cavity positioning; and v) gas pressure.

Luminescence properties of an orange-red phosphor GdAl3(BO3)4:Sm3+ under VUV excitation and energy transfer from Gd3+ to Sm3+

In order to develop a new warm-color emission phosphor under vacuum ultraviolet (VUV) excitation, trivalent samarium ion (Sm3+) doped GdAl3(BO3)4 was prepared by a solid state reaction technique at high temperature. The VUV excitation and emission spectra of as-synthesized sample GdAl3(BO3)4:Sm3+ were determined in the Beijing Synchrotron Radiation Facilities (BSRF). Compared with the emission of GdAl3(BO3)4:Eu3+, GdAl3(BO3)4:Sm3+ shows an orange-red emission under Xe 172nm VUV excitation, which indicates that Sm3+ ion can be a possible activator to obtain warm color emission in the field of lighting. Furthermore, for improving the emission of Sm3+ doped in GdAl3(BO3)4, the energy transfer process from Gd3+ in the host to the activator Sm3+ was investigated through the analysis of spectroscopic characteristics and luminescence decay curves of GdAl3(BO3)4:Sm3+. The results reveal that there exists energy transfer from Gd3+ to Sm3+, but the energy transfer from Sm3+ to Gd3+ is inefficient.

VACUUM ULTRAVIOLET EMISSION SPECTRUM MEASUREMENT OF A MICROWAVE-DISCHARGE HYDROGEN-FLOW LAMP IN SEVERAL CONFIGURATIONS: APPLICATION TO PHOTODESORPTION OF CO ICE

We report measurements of the vacuum ultraviolet (VUV) emission spectra of a microwave-discharge hydrogen-flow lamp (MDHL), a common tool in astrochemistry laboratories working on ice VUV photoprocessing. The MDHL provides hydrogen Ly-α (121.6 nm) and H2 molecular emission in the 110-180 nm range. We show that the spectral characteristics of the VUV light emitted in this range, in particular the relative proportion of Ly-α to molecular emission bands, strongly depend on the pressure of H2 inside the lamp, the lamp geometry (F type versus T type), the gas used (pure H2 versus H2 seeded in He), and the optical properties of the window used (MgF2 versus CaF2). These different configurations are used to study the VUV irradiation of CO ice at 14 K. In contrast to the majority of studies dedicated to the VUV irradiation of astrophysical ice analogs, which have not taken into consideration the emission spectrum of the MDHL, our results show that the processes induced by photons in CO ice from a broad energy range are different and more complex than the sum of individual processes induced by monochromatic sources spanning the same energy range, as a result of the existence of multistate electronic transitions and discrepancy in absorption cross sections between parent molecules and products in the Ly-α and H2 molecular emission ranges.

Microdischarge Process and Vacuum Ultraviolet Emission Properties of Dielectric-Barrier-Discharge-Type Flat Fluorescent Lamps

The microdischarge process and the vacuum ultraviolet (VUV) emission properties of dielectric-barrier-discharge-type flat fluorescent lamps (FFLs) are investigated by shooting the spatiotemporally resolved images of a microdischarge in an FFL filled with Ne-Xe (10%) gas mixture of 85 kPa with a high-speed intensified charge-coupled device camera and by measuring the VUV emission spectra at various gas pressures and driving parameters with a vacuum monochromator and a photomultiplier tube. It was found that a microdischarge was generated at a protrusion on the cathode at first, diffused to the anode side afterward, and exhibited a uniform glow discharge pattern. The measured results of the VUV spectra show that, as the total gas pressure increases, the 147-nm resonance emission gradually decreases, while the continuum emission centered at 173 nm rapidly increases, which cause both of the intensity and the efficiency of the VUV emission to increase. As the driving voltage amplitude increases, there exists a maximum VUV emission efficiency value. At a total gas pressure of 70 kPa, as the driving pulse frequency increases from 50 to 130 kHz, the spectral intensities of the VUV emission initially increase and then gradually tend to saturate at 90 kHz.

5d-4f luminescence of Nd3+, Gd3+, Er3+, Tm3+, and Ho3+ ions in crystals of alkaline earth fluorides

The vacuum ultraviolet emission spectra of alkaline-earth fluoride (CaF2, SrF2, BaF2) crystals with rare earth impurity ions (Nd, Gd, Er, Tm, Ho) have been investigated. The main luminescence bands are described well by the transitions from the lowest excited 5d state to different 4f levels of rare earth ions.

Dissociative excitation and fragmentation of S8 by electron impact

The vacuum-ultraviolet emission spectrum from 136 nm to 168 nm following the dissociative excitation of a predominantly S(8) target by electron impact at 100 eV incident energy was measured. The relative cross sections for the dominant multiplets at 138.9, 142.9, 147.9, and 166.7 nm are presented. Excitation functions are shown for electron-impact energies from below threshold to 360 eV for the two most prominent emissions at 142.5 nm and 147.4 nm. Five thresholds are clearly apparent in both excitation functions. For the four highest energy channels, the energy separation between the adjacent thresholds is approximately constant and the cross sections reduce regularly as the threshold energies increase. We suggest possible fragmentation pathways of the dissociating S(8) molecule that reproduce the energies of our observed thresholds.

Photoresist modifications by plasma vacuum ultraviolet radiation: The role of polymer structure and plasma chemistry

While vacuum ultraviolet (VUV) photon irradiation has been shown to significantly contribute to material modifications of polymers during plasma exposures, the impact of radiation-induced material alterations on roughness development during plasma processing has remained unclear. The authors have studied the interaction of the radiation of Ar and C4F8/Ar plasma discharges with 193 and 248 nm advanced photoresists (PRs). Optical filters were used to vary the radiation exposure wavelength range in the ultraviolet (UV) and VUV emission spectra. This enables clarification of the respective roles of plasma photon radiation wavelength and PR polymer structure on the chemical and structural changes produced in the materials. Chemical changes in polymer composition at the film surface and in the material bulk were determined by vacuum transfer x-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy. Morphological changes, film thickness reduction, and changes in surface and pattern morphology were characterized by ellipsometry, scanning electron microscopy, and atomic force microscopy. The exposure of methacrylate based 193 nm PR to photon radiation in the UV/VUV spectral range (λ=112–143 nm) leads to detachment and removal of oxygen containing polymer pendant groups to a depth of about 200 nm. This causes changes in the polymer structure by chain scission, significant film thickness reduction, and reduced pattern critical dimensions and line edge roughness. Chain-scission reactions and residual detached polymer pendant groups are expected to effectively soften layers of 193 nm PR. In contrast to 193 nm PR, styrene based 248 nm PR was found to be significantly more stable under plasma-produced irradiation due to the low oxygen content, low ester linkage concentration, and absence of lactone. Small thickness reduction, reduced oxygen loss, and cross-linking were observed in the surface region of 248 nm PR. Radiation-induced material modifications of both PR materials decreased with increasing photon wavelength in Ar discharges. Increasing modification of 193 nm PR was observed for increasing photon flux at higher wavelengths (λ=143–300 nm) by the emission characteristic of fluorocarbon containing plasmas. In C4F8/Ar plasma, the authors observed strongly increased loss of oxygen at the film surface and in the COC and CO lactone bonds in the material bulk along with film thickness reduction compared to pure Ar discharges. These modifications are directly relevant to plasma processes used for pattern transfer, which often contain fluorocarbon species.

Fabrication and photoluminescence characteristic of Pr:LuAG scintillator ceramics

Abstract 0.5at% Pr:LuAG transparent ceramics was fabricated by a solid state reaction method. The transmission of the ceramics beyond 310 nm reaches to around 75%. When excited by ultraviolet (UV) and vacuum ultraviolet (VUV) light, the domain emission near 309 nm was observed which was due to the 5d–4f radiative transition of Pr3+. Its photoluminescence decay time is about 19 ns. VUV excitation and emission spectrum at 14 K and 289 K respectively reveal the existence of defects and other centers, which are sensitive to temperature and anneal process.

VUV emission spectra in charge-exchange collisions of multiply charged Sn ions with rare gases

We have measured the VUV (vacuum ultraviolet) emission spectra following charge transfer collisions of Snq+(q = 3-6) with neutral rare gas targets at collision energies of 50–100 keV. To understand the emission lines in observed spectra, we have executed the GRASP92 and RATIP programs, which provide both emission wavelengths and transition probabilities between the excited states of the Sn5+ ions.

Spectral Band Shifts in the Electronic Spectra of Rare Earth Sesquioxide Nanomaterials Doped with Europium

The UV―visible and vacuum ultraviolet emission and excitation spectra of Y 2 O 3 :Eu 3+ (1 and 0.1 atom %) nanomaterials, prepared by combustion syntheses with use of glycine or hydrazine, have been recorded in order to investigate spectral band shifts as a function of particle size. FT-IR spectra and site-selective emission spectra at low temperature show the presence of impurities for all of these samples, with the least impurities for the samples prepared using stoichiometric ratios of reactants, where (i) the relative intensity of the free exciton (FE) and the charge transfer (CT) bands changes significantly with Eu 3+ concentration, (ii) there is a small red-shift of the CT band position with decreasing particle size, and (iii) the shifts of the FE and band-to-band (CB) transitions are within a separation of 116 cm ―1 (14 meV) at room temperature for samples of size 20-40 nm. The band positions change for samples synthesized when not using stoichiometric ratios of reactants.

Vacuum ultraviolet spectra in charge transfer collisions of multiply charged Sn ions

We measured the vacuum ultraviolet (VUV) emission spectra following charge transfer collisions of Snq+ (q = 3-6) with neutral rare gas targets at collision energies of 50-100 keV. We identified some of emission lines from reported energy levels. Several lines were observed in collisions of different charge states of ions. This finding means that the multiple-electron capture processes can take place effectively in our experiment. Significant target dependences were observed in the spectra with the projectile of Sn4+ and Sn6+.

VUV luminescence properties of Y 0.95Eu 0.05PO 4 phosphor derived by a modified solid-state route

A modified solid-state route was attempted to prepare Y 0.95 Eu 0.05PO 4 PDP phosphor, involving milling a powdered mixture of YCl 3, EuCl 3, and (NH 4) 2HPO 4 and calcining the milling-derived precursor. The thermal decomposition behavior of the milling-derived precursor was investigated by thermogravimetric analysis (TGA). Phase compositions, morphologies, and luminescence properties of the prepared phosphor powder were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and vacuum ultraviolet (VUV) emission spectra, respectively. The results indicated that the Y 0.95Eu 0.05PO 4 phosphor powder obtained at a calcination temperature of 900°C was xenotime-structured. The phosphor powder particles were uniform and spherical-shaped with a primary particle size of ∼200 nm. In comparison with that derived by the conventional solid-state route, the phosphor powder prepared by the modified solid-state route exhibited a higher color purity, presenting a predominant emission peak at 619 nm under 147 nm VUV excitation.

High resolution vacuum ultraviolet emission spectrum of D2: The B′Σu+1→XΣg+1 band system

In this work, we have extended our previous high resolution study of the vacuum ultraviolet emission spectrum of the D2 molecule [M. Roudjane, et al. J. Chem. Phys. 125, 214305 (2006)] up to 124.2 nm in order to investigate the B' 1Sigmau+-->X 1Sigmag+ band system. The analysis of the spectrum has been carried out by means of a complex spectrum visual identification code IDEN [V. I. Azarov, Phys. Scr. 44, 528 (1991); 48, 656, (1993)] and supported by theoretical calculations using ab initio data [L. Wolniewicz, J. Chem. Phys. 103, 1792 (1995); 99, 1851 (1993); G. Staszewska and L. Wolniewicz, J. Mol. Spectrosc. 212, 208 (2002); L. Wolniewicz and G. Staszewska, 220, 45 (2003)] which provided level energies and transition probabilities. More than 1480 new emission lines have been observed and 109 bands belonging to the B' 1Sigmau+-->X 1Sigmag+ system have been identified between 84.1 and 121.6 nm. Except for the upsilon'-0 bands that were reported in absorption [I. Dabrowski and G. Herzberg, Can. J. Phys. 52, 1110 (1974)], all the upsilon'-upsilon" bands are reported here for the first time. The analysis led to the determination of 111 rovibronic energy levels in the B' 1Sigmau+ state, of which 31 with higher rotational numbers J are new. Observed perturbations are accounted for through a set of coupled equations involving the four excited electronic states B 1Sigmau+, B' 1Sigmau+, C 1Piu, and D 1Piu and including nonadiabatic couplings. The solution of this set provides the percent contribution of these four states to each of the observed rovibronic level.

Downconversion in Cs 2NaErCl 6

The room temperature downconversion emission of Er 3+ in the low phonon energy, low band-gap host Cs 2NaErCl 6 upon synchrotron radiation excitation is rationalized. Energy transfer cross-relaxation schemes are proposed following the interpretation of the vacuum ultraviolet and ultraviolet excitation and emission spectra. The highest energy emission from Er 3+ occurs from the 2I 11/2 multiplet term (∼40600 cm −1). The behaviour of Er 3+ in Cs 2NaYCl 6:Er 3+ is also discussed and interpreted.

High resolution vacuum ultraviolet emission spectrum of D2 from 78to103nm: The DΠu1→XΣg+1 and D′Πu−1→XΣg+1 band systems

The emission spectrum of the D2 molecule has been studied at high resolution in the vacuum ultraviolet region 78.5–102.7nm. A detailed analysis of the two DΠu1→XΣg+1 and D′Πu−1→XΣg+1 electronic band systems is reported. New and improved values of the level energies of the two upper states have been derived with the help of the program IDEN [V. I. Azarov, Phys. Scr. 44, 528 (1991); 48, 656 (1993)], originally developed for atomic spectral analysis. A detailed comparison is made between the observed energy levels and solutions of coupled equations using the newest ab initio potentials by Wolniewicz and co-workers [J. Chem. Phys. 103, 1792 (1995); 99, 1851 (1993); J. Mol. Spectros. 212, 208 (2002); 220, 45 (2003)] taking into account the nonadiabatic coupling terms for the DΠu1 state with the lowest electronic states BΣu+1, CΠu1, and B′Σu+1. A satisfactory agreement has been found for most of the level energies belonging to the D and D′ states. The remaining differences between observation and theory are probably due to nonadiabatic couplings with other higher electronic states which were neglected in the calculations.

Low Temperature Luminescence Properties of Tm 3+ Doped Aluminate Phosphor

(Ba 0.66Sr 0.33)Mg 0.8Al 11.47O 19: Tm 0.01 3+ (BSMA:Tm 3+) phosphor was synthesized by solid-state reactions. The sample was characterized by X-ray diffraction (XRD), scanning electronic microscope (SEM), vacuum ultraviolet (VUV) spectra, ultraviolet (UV) spectra and FT-IR spectrum. XRD pattern reveals that BSMA:Tm 3+ has the same structure as BaAl 12O 19 phase. SEM image illustrates that the phosphor has the hexagonal shape and deep slice structure. VUV and UV emission spectra at 20, 50 and 100 K show that the low temperature luminescence intensities become weak gradually with the increasing of the temperature under 147 and 254 nm excitation. The strong broadband peaks at around 357 and 397 nm and the peak at 516 nm under 147 nm excitation all correspond to the characteristic transitions of Tm 3+ ions. However, under UV (254 nm) excitation, the main peak becomes 530 nm which has very high line intensity, and the peaks at about 362 and 403 nm are very weak. The excitation spectrum at 20 K shows that there are three absorption peaks at around 153, 186 and 193 nm when 516 nm emission is monitored. The absorption peaks of [AlO 4], [AlO 6] and Al-O can be observed in FT-IR spectrum.