Multiple M‐Effect Signal in Noble Gases and Hydrogen Mixture Discharge

The M‐effect (monochromatization‐effect) is a powerful process which can give high intensity monochromatic spectra with a certain wavelength depending on the type of used gas mixtures to generate the plasma state. The effect consists in the emission of a single spectral line emerging from plasma under specific experimental conditions involving one electropositive gas and one electronegative gas mixture. For example, in the case of Ne‐H₂ mixture, a clear monochrome radiation was obtained, corresponding to the λ_Ne =585.3 nm wavelength at 2p₁‐1s₂ transition in the Paschen notation, the pressures ranging between 10‐100 torr. In this paper we prove the general character of this effect, i.e. if the optical emission spectra (OES) reduced to selective lines can be noticed also in other multiple gas mixture discharges. The Ne‐Ar‐Xe mixture discharges with different percentages of H2 as electronegative gas added in has been investigated. The triple M‐effect, means three specific monochromatic lines, could be revealed in the OES at 50% of H2 addition in Ne‐Ar‐Xe mixture (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Temporal extension of stable glow discharges in fluorine-based excimer laser gas mixtures by the addition of xenon

The effect of addition of xenon on the long term homogeneity of discharges in F₂and ArF excimer laser gas mixtures was investigated in a small-volume discharge chamber. The gas mixture in the discharge chamber was preionized by X-rays. A special electrical excitation circuit containing a pulse forming line provided a long, square-shaped current pumping pulse of a predetermined duration to the discharge electrodes. The initiation and the development of the discharge was monitored via its fluorescence signal with an intensified CCD camera. We found that adding Xe up to partial pressures of 0.53 mbar extended the homogeneous phase of the discharge from 80 ns to approximately 200 ns in He/F₂as well as in He/Ar/F₂and Ne/Ar/F₂excimer laser gas mixtures. Monitoring of the ArF and XeF spontaneous emission signals showed that the formation of ArF excimers remained unaffected by the addition of xenon (up to 1.3 mbar) to the laser gas mixture.     

Spectroscopic diagnostics of barrier discharge plasmas in mixtures of zinc diiodide with inert gases

The spectral characteristics of the emission of gas discharge atmospheric pressure plasmas in mixtures of zinc diiodide vapor with inert gases (He, Ne, Ar, Kr, and Xe) are investigated. The formation of a gas discharge plasma and the excitation of the components of a working mixture were performed in a high-frequency (with a repetition frequency of sinusoidal voltage pulses of 100 kHz) barrier discharge. The gas discharge emission was analyzed in the spectral range 200–900 nm with a resolution of 0.05 nm. Emission bands of ZnI(B-X) exciplex molecules and I₂* excimer molecules, lines of inert gases, and emission bands of XeI* exciplex molecules (in Xe-containing mixtures) were revealed. It is ascertained that the strongest emission of ZnI* molecules is observed in ZnI₂/He(Ne) mixtures. The regularities in the spectral characteristics of the gas discharge plasma emission are considered.     

A Miniaturized XeCl Dielectric Barrier Discharge as a Source of Short Lived,Fast Decaying UV Radiation

A dielectric barrier discharge (DBD) of coaxial geometry has been examined as source of intensive, short‐lived UV radiation. A binary gas mixture consisting of 98% Xe + 2% Cl₂ and a ternary composition of 96% Ne + 6% Xe + 0.2% HCl were investigated in the pressure range between 10 and 750 mbar. The discharge was excited by unipolar high voltage square pulses with amplitudes of 3 to 7 kV at a repetition rate of 100 Hz. UV radiation intensity is increased by combining 5 square pulses with a period of 1 μs each in one train (burst). Radiation decay on three orders of magnitude within 10 μs was obtained for both gas mixtures in burst mode. Maximum energy of the light pulse was the same for both gas mixtures and estimated as 40 nJ. It is shown that the optimum gas pressure for highest radiation intensity depends not only on gas composition but also on applied voltage and number of pulses in the train. A variation of the spectral band shape of XeCl emission during the pulse is detected (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Dynamics and correlated performance of a photo-triggered discharge-pumped HF laser using SF6 with hydrogen or ethane

3 , has been performed in Ne/SF₆/H₂ and Ne/SF₆/C₂H₆ mixtures. Parameters involved have been the storage line capacitance and the circuit inductance, the capacitors charging voltage, the RH-molecule type and partial pressure, and the X-ray dose for the preionization. High laser performance has been achieved with C₂H₆: an output energy up to 3 J corresponding to a specific energy of 9.6 J/l at an efficiency of 4.7%, which strengthens the advantage of the photo-triggering technique to energize high-power HF lasers. However the optimum performance achieved with H₂, 5.75 J/l and 3.5%, are lower. It is shown, through a time-resolved study of the electrical discharge and spatial dynamics correlated to laser power and energy measurements, that discharge instabilities are responsible for the poor laser performance of the mixture with H₂. These instabilities, which lead to arc development, are characteristics of the discharge in Ne/SF₆. It is demonstrated for the first time that addition of a heavy hydrocarbon, such as C₂H₆, to that mixture induces the discharge stabilization so that the laser emission arises in a homogeneous active medium. This effect allows us to achieve better laser performance than with H₂. Received: 17 March 1998/Revised version: 13 July 1998     

Spectroscopic diagnostics of barrier-discharge plasma in mixtures of cadmium diiodide vapor with gases

The spectral characteristics of the emission of atmospheric-pressure gas-discharge plasma in mixtures of cadmium diiodide vapor with gases (Ne, Ar, Kr, Xe, and N₂) were investigated along with the time characteristics of the voltage and current. The gas-discharge plasma was produced and excited by a barrier discharge at a repetition rate of sine voltage pulses of up to 140 kHz. The discharge emission was analyzed in the spectral range 200–900 nm with a high resolution (0.05 nm). Radiation from exciplex CdI(B-X) molecules and excimer I₂* molecules was revealed, as well as the atomic lines of cadmium, iodine, and inert gases. In a mixture with xenon, radiation from exciplex molecules XeI(B-X, B-A) was also found. This radiation prevailed in the spectra at mixture temperatures up to 150°C. The further increase of the temperature leads to the prevalence of the CdI(B-X) radiation. It was found that the most intense CdI(B-X) radiation is observed in mixtures CdI₂/Xe(N₂)/Ne. Regularities in the spectral characteristics of the emission of the gas-discharge plasma are discussed.     

Diagnostics of a Compact Discharge-Pumped XeCl Laser with BCl3 Halogen Donor

The results of a comprehensive study of a compact UV-preionized XeCl laser are presented. The subjects of this study were: discharge voltage and current measurements, dye laser probing of the active medium, and the mass spectrometry of gas mixture degradation products. It is shown that the gas lifetime was significantly improved when the laser was operated with BCl₃ as a halogen donor instead of commonly used HCl. By the dye laser absorption and gain probing, the temporal and spatial dependences of the densities for several plasma components, Ne*, Xe*, Xe⁺*, Cl^–, XeCl* and of ground state boron atoms were measured. Some aspects of plasma kinetics for uniform and constricted phases of the discharge are discussed. By the mass spectrometry of gas mixture degradation products on long-term operation of the laser device several gaseous (N₂, O₂, CO₂, H₂O, C₂H₄) and solid (NiCl₂, H₃BO₃) products were detected in the laser chamber. NH₄Cl was determined to be a stable fraction of the deposits on optics surfaces. The reasons for the improvement of gas lifetime for BCl₃-containing gas mixtures are discussed.     

Na 32P-32D line broadening by Ne,Ar, and Xe

The normalized emission intensity in the wings of the optically thin Na 3²P-3²D lines broadened by Ne, Ar, and Xe has been measured in emission from a high-pressure discharge. A blended satellite occurs about 80 cm^-1 into the Na-Xe red wing and a progression of increasing red wing intensity from Ne to Ar to Xe is observed. Xe densities of 2.5 and 9.1 × 10¹⁹ cm^-3 were used, and the pressure dependence of the NaXe line shape indicates that multiple perturber interactions are important in the far wing at the higher noble gas densities.     

Influence of Small Xe Additives on the Detonation Threshold for O<Subscript>2</Subscript>−H<Subscript>2</Subscript>−He Mixtures

The effect of a small Xe additive on the conditions of detonation initiation in incident shock waves of various intensities is studied. The experiments are carried out on a shock tube facility with 10% H₂ + 5% O₂ + 85% He, 10% H₂ + 5% O₂ + 84.75% He + 0.25% Xe, and 10% H₂ + 5% O₂ + 84.5% He + 0.5% Xe mixtures. The addition of Xe led to a shift in the detonation threshold toward weaker shock waves. This effect is probably due to a significant increase in the frequency of high-energy collisions between O₂ and Xe molecules in the shock wave front in comparison with that characteristic of the equilibrium behind the wave, a factor that significantly accelerates the chemical reaction between O₂ and H₂ behind the front. The effect is a consequence of the formation of a specific translational nonequilibrium in the wave front. A previously performed numerical study of the distributions of pairs of O₂ and Xe molecules in the shock wave front shows that this effect can be enhanced by decreasing the Xe concentration from 0.5 to 0.25%. The experiment performed indirectly confirms this conclusion. It turns out that, for the mixture with 0.25% Xe, the detonation threshold shifts more strongly to the region of weaker shock waves than for the mixture with 0.5% Xe. This result gives additional arguments in favor of the assumption that this effect is due to the specifics of the translational nonequilibrium in the wave front.     

High energy collisions of protonated water clusters

We have measured attenuation cross sections and fragmentation cross sections for protonated water clusters H(H₂O)_n ⁺ (n = 1 to 100) colliding with noble gas atoms (He and Xe) at a laboratory energy of 50 keV. In collisions with He, a transparency effect in the attenuation cross section was observed. For the case of fragmentation in collisions with Xe, a strong enhancement of small clusters was observed which we attribute to multifragmentation. Received 30 November 2000     

First applicability of ZnGa2O4 : Ge, Li, Mn phosphor for a plasma display panel

The green emission intensity of ZnGa₂O₄:Ge⁴⁺, Li⁺, Mn²⁺ excited by the vacuum ultraviolet line of 147 nm reaches 70% of commercial green Zn₂SiO₄:Mn²⁺. The vacuum ultraviolet excitation spectra consist of four peaks. In a plasma display test bed filled with Ar and Ne plasma discharged by a radio-frequency generator of 13.6 MHz, ZnGa₂O₄:Ge⁴⁺, Li⁺, Mn²⁺ and commercial Zn₂SiO₄:Mn²⁺ phosphor screens show a linear increase in luminance with increasing self bias voltages. Increasing gas pressures cause the luminance to increase. Also, on increasing the self bias voltages and the gas pressures, the current densities of ZnGa₂O₄:Ge⁴⁺, Li⁺, Mn²⁺ phosphor screens are increased; this is the same behavior as that of the commercial phosphor.     

Electrical and optical characterization of pulsed plasma of N<Subscript>2</Subscript>–H<Subscript>2</Subscript>

This paper considers the electrical and optical characterization of glow discharge pulsed plasma in N₂/H₂ gas mixtures at a pressures range between 0.5 and 4.0 Torr and discharge current between 0.2 and 0.6 A. Electron temperature and ion density measurements were performed employing a double Langmuir probe. They were found to increase rapidly as the H₂ percentage in the mixture was increased up to 20%. This increase slows down as the H₂ percentage in the gas mixture was increased above 20% at the same pressure. Emission spectroscopy was employed to observe emission from the pulsed plasma of a steady-state electric discharge. The discharge mainly emits within the range 280–500 nm. The emission consists of N₂ (C-X) 316, 336, 358 nm narrow peaks and a broad band with a maximum at λ_max = 427 nm. Also lines of N₂, N₂ ⁺ and NH excited states were observed. All lines and bands have their maximum intensity at the discharge current of 0.417 A. The intensities of the main bands and spectral lines are determined as functions of the total pressure and discharge current. Agreement with other theoretical and experimental groups was established.     

Electronic and geometric structure of doped rare-gas clusters: surface, site and size effects studied with luminescence spectroscopy

The electronic and geometric structure of rare gas clusters doped with rare-gas atoms Rg = Xe, Kr or Ar is investigated with fluorescence excitation spectroscopy in the VUV spectral range. Several absorption bands are observed in the region of the first electronic excitations of the impurity atoms, which are related to the lowest spin-orbit split atomic ³P₁ and ¹P₁ states. Due to influence of surrounding atoms of the cluster, the atomic lines are shifted to the blue and broadened (“electronical cage effect”). From the known interaction potentials and the measured spectral shifts the coordination of the impurity atom in Ar_N, Kr_N, Ne_N and He_N could be studied in great detail. In the interior of Kr_N and Ar_N the Xe atoms are located in substitutional sites with 12 nearest neighbours and internuclear distances comparable to that of the host matrix. In Ne_N and He_N the cluster atoms (18 and 22, respectively) arrange themselves around the Xe impurity with a bondlength comparable to that of the heteronuclear dimer. The results confirm that He clusters are liquid while Ne clusters are solid for N≥ 300. Smaller Ne clusters exhibit a liquid like behaviour. When doping is strong, small Rg_m-clusters (Rg = Xe, Kr, Ar, m≤10 ²) are formed in the interior sites of the host cluster made of Ne or He. Specific electronically excited states, assigned to interface excitons are observed. Their absorption bands appear and shift towards lower energy when the cluster size m increases, according to the Frenkel exciton model. The characteristic bulk excitons appear in the spectra, only when the cluster radius exceeds the penetration depth of the interface exciton, which can be considerably larger than that in free Rg_m clusters. This effect is sensitive to electron affinities of the guest and the host cluster.     

Experimental verification of a zero-dimensional model of the kinetics of XeCl* discharges by XeCl*(B)-, XeCl*(C)-, and Xe2Cl*-density measurements

Absolutely calibrated emission spectroscopy has been used to determine the particle number densities of XeCl^*(B), XeCl^*(C), and Xe₂Cl^* in a small scale Ne/Xe/HCl discharge with well-defined current and voltage pulses for a wide range of parameters. The measured particle number densities could be reproduced quite well by numerical model calculations using the rate-coefficient values of Quiñones et al. [1] for the quenching of XeCl^*(B,C) by Ne, Xe, and 2Xe, but 3.0 × 10^–31 cm⁶/s for the formation of Xe₂Cl^* by (Ne + Xe)-quenching. For the electron quenching, we recommend a rate coefficient value of 3.2 × 10^–8 cm³/s. From the equilibrium ratio of the particle number densities of XeCl^*(C) and XeCl^*(B), the energy separation between these states has been estimated to be 72 ± 33 cm^–1 with the B state placed above the C state.     

Charge transfer from the ground state of muonic hydrogen to at room temperature

The present status of research of muon transfer from the ground state of muonic protium to ⁴He is reviewed. The analysis of a recent measurement in a triple gas mixture of H₂+⁴He+Ne at 15 bar and room temperature is presented and the result is compared to the existing experimental and theoretical rates. The average muon transfer rate from protium to ⁴He determined from all lifetime measurements is . Received: 22 January 1998 / Revised: 4 March 1998 / Accepted: 31 March 1998     

Singlet-triplet excitation ratios in Ne III, Ar III and N II under ion impact

Peculiar properties of ion-atom collision systems, in particular deviations from statistical populations of singlet and triplet levels, can be studied by optical spectroscopy. We have extended earlier studies by VUV spectroscopy of a number of collision systems at various collision energies in the 0.01-MeV/nucleon to 1-MeV/nucleon range, involving H₂ ⁺, H⁺, He⁺, He²⁺, Ne⁺, Ar⁺, and N₂ ⁺ as projectiles and Ne, Ar, and N₂ as target gases. Statistically significant deviations of the relative intensities of singlet and triplet lines from simple ratios are observed in the displaced terms of the valence shell of Ne III, corroborating and extending earlier work. For Ar III, the energy dependences of singlet-to-triplet excitation ratios are very different for different projectiles. For N II, in contrast, all observed line ratios are practically independent of the projectile energy. Received 17 November 2000 and Received in final form 31 January 2001     

H1+,H2+,H3+和He,Ne,Ar碰撞过程中的巴耳末系Hα,Hβ,Hγ发射

实验利用TN-1710光学多道分析系统(OMA),对H₁⁺,H₂⁺,H₃⁺和He,Ne,Ar碰撞过程中产生的巴耳末系H_α,H_β,H_γ发射进行了测量,入射离子H₁⁺,H₂⁺,H₃⁺的 关键词：     

NIR to visible upconversion emission from Dy: ZBLYAN glasses

This paper reports on the near infrared (730-783 nm) to the visible upconversion emissions at 482 nm (⁴F_9/2→⁶H_15/2), 576 nm (⁴F_9/2→⁶H_13/2) and 662 nm (⁴F_9/2→⁶H_11/2) from the Dy³⁺doped 53ZrF₄-20BaF₂-2LaF₃-2YF₃-3AlF₃-19NaF-1DyF₃ glasses. We have also carried out a systematic study on the normal emission properties of these glasses in order to understand their performance both as a NIR upconverted visible luminescent and as normal visible fluorescent optical systems of technical importance. With an increase in Dy³⁺ concentration beyond a particular value (1 mol%), activator-activator interaction becomes a significant cause of concentration quenching in the luminescence properties. The dependence of the emission spectra on the excitation wavelengths has also been examined and 451 nm was found to be the ideal excitation wavelength in the measurement of normal fluorescence spectra. In the case of NIR upconverted visible emission, we have observed that the NIR excitation at 783 nm as the suitable pump wavelength in demonstrating prominent visible emission colours from these glasses. The relevance in undertaking these optical materials lies in their potential for upconversion laser application in the visible wavelength region. The NIR upconversion phenomenon has been explained in terms of energy level schemes due to excited state absorption (ESA) and energy transfer upconversion (ETU) processes.     

溶胶-凝胶制备ZnO-SiO2复合膜的量子效应和上转换发光

采用溶胶-凝胶技术在玻璃衬底上制备了ZnO薄膜和ZnO-SiO₂复合膜.原子力显微镜照片显示ZnO薄膜具有球状纳米晶粒;可见光-紫外透射光谱表明ZnO-SiO₂复合膜在可见光区的透过率大约是85%,透过率从330 nm开始下降,到290 nm附近降为零.由于量子效应,吸收边出现明显的蓝移.在室温下用不同波长的光激发ZnO-SiO₂复合膜,光致发光谱显示ZnO-SiO₂复合膜对应于激子发射的290 nm附近的紫外发光峰与透射谱所显示的吸收边位置一致,没有出现斯托克斯红移.同时,ZnO-SiO₂复合膜出现了双光子和三光子吸收现象和上转换发光现象. 关键词： 2')" href="#">ZnO-SiO₂ 量子效应 双光子和三光子吸收 上转换发光     

Gas-discharge XeF* (B→X) laser with high specific output energy

The discharge characteristics of the XeF* (BX) laser are investigated. The NF₃ and Xe partial pressure of the laser gas mixture and the total gas pressure have been varied. A highest specific output energy of 4.7 J/l with an efficiency of 0.5% was obtained from a X-ray preionized Ne/Xe/NF₃ gas mixture at 6 bar with single-pulse excitation through a multichannel spark gap.