Decay times of the intrinsic luminescence band (1750 Å) of solid Xe

Thin films of solid xenon have been excited by a pulsed electron beam with electron energies of 300 eV and pulse lengths down to 5 nsec at low current. For the main luminescence band of solid xenon (λ ≈ 1750 Å) two decay times have been observed. The short decay time (3 ± 1 nsec) is independent of temperature between 4 K and 30 K, whereas the long decay time decreases from 900 ± 50 nsec at 4 K to 150 ± 50 nsec at 30 K.     

Luminescence spectra of solid xenon excited by volume discharge

The luminescence spectra of solid xenon excited by a volume discharge are studied for the first time. The majority of the energy is emitted in the VUV spectral region due to the radiative decay of excitons. A specific feature of the spectra in the UV and visible regions is the complete absence of lines belonging to neutral excited particles (one-center Xe* and two-center Xe ₂ ^* excitons) and to diatomic Xe ₂ ⁺ ions. Numerous lines of the Xe⁺ ion are shifted by 0.1–0.3 nm with respect to their positions in the gas; the larger the shift, the stronger the distortion of the line shape. Based on the data obtained, a mechanism by which solid xenon is excited and ionized by fast drifting electrons is proposed.     

Luminescence decay kinetics of Eu<Superscript>3+</Superscript> ions in phosphate glasses of different composition under photo- and electron excitations

The influence of matrix composition, coactivators, and excitation method on the luminescence kinetics of Eu³⁺ ions in lithium–phosphate and lithium–phosphate–borate glasses activated by Eu, Eu/Tb, and Eu/Dy is studied. Luminescence is excited by a high current electron beam and a xenon lamp. It is found that, under photoexcitation, the europium luminescence decays more slowly than under electronic excitation. Depending on the content of cation modifiers ZnO and Li₂O, the decay time decreases with increasing amount of ZnO. The decay time weakly depends on the europium concentration. The decay of the luminescence of europium ions is well described by the Inokuti–Hirayama model.     

Ultrahot electron formation under excess electron drift through solid Xe

The formation of "hot" (8 eV) electrons under excess electron drift in a moderate electrostatic field through solid xenon has been experimentally proved by observation of secondary electrons emitted from the photocathode. At T=77 K and U=1000 V one drifting electron produces about 20 (172 nm) photons, the efficiency of electric field-to-vacuum ultraviolet emission conversion is 15% tending to grow with temperature. A self-sustained electric discharge has been generated in solid Xe using a three-electrode cell with a zinc cathode.     

On the nature of emission bands of self-trapped excitons in solid xenon

The paper presents the analysis of experimental data on the temperature dependence of luminescence spectra of solid xenon. The mechanisms of exciton self-trapping down to quasi-molecular states under different conditions are discussed. A new treatment of spectral distribution of intensity through quasi-molecular luminescence bands is proposed; according to the treatment, at T < 55 K the emission is associated with the transition from the lowest vibrational relaxation excited state ³Σ_u⁺, while at T 60 K from the term ¹Σ_u⁺. Spectral redistribution of intensities in the 60–150 K range is due to an increase in the rate of vibrational relaxation in the state ¹Σ_u⁺ with increasing the crystal temperature.     

Transition bidimensionnelle du premier ordre; cas du xénon adsorbé sur la face (0001) du graphite

Submonolayer adsorption isotherms of xenon condensed on the (0001) face of graphite are measured between 85°K and 102°K by Auger electron spectroscopy. A two-dimensional phase change 2D gas ? 2D solid is emphasized. The solid phase is characterized by low energy electron diffraction. It is a two-dimensional crystal in epitaxy on the graphite. The analysis of the adsorption isotherms measured with a sensivity of $\text{1}\text{500}$ of monolayer, i.e. 10¹⁰ atoms, allows to determine the integral heat of adsorption at the two-dimensional phase change (5.5 ± 0.1 kcal mole^?1). We also deduced from our measurements, the binding energy of an individual atom of xenon on the (0001) face of graphite, the heat and the entropy of fusion of the two-dimensional crystal.     

Electron beam effects in auger analysis of physisorbed xenon

Adsorbed xenon on evaporated films of nickel and platinum has been analysed by Auger electron spectroscopy. The primary electron beam is shown to cause some surface heating resulting in a displacement of the isotherms. This temperature effect is the same for both metals and is due to the limiting thermal conductivity of the glass substrate. A further effect, the electron induced desorption (EID) of xenon is evidenced by a distortion of the isotherms at low equilibrium gas pressures. This effect is more clearly observed on platinum because the coverage is higher than on nickel. The EID cross-section for xenon on both metals is found to be 1 × 10^?17cm². The attenuation of the metal Auger peaks by the xenon overlayer is found to be less for platinum than for nickel. This difference is attributed to a lower packing density of xenon on the platinum surface.     

Experimental investigations of the formation of XeF*(B 2II1/2) excimer molecules during the injection of SF6 into a xenon plasma flow

The luminescence of XeF*(B ²II_1/2) molecules from a zone formed in the injection of SF₆ gas into a freely flowing xenon plasma jet is investigated. The experiments show that both the energy characteristics of the luminescence and the geometrical dimensions of the plasmachemical reaction zone can be controlled by varying the power input to the plasmatron and the mass flow rates of SF₆ and the xenon plasma. It is shown that the main contribution to the production of XeF*(B ²II_1/2) excimer molecules under the given experimental conditions is from two-particle ion-ion reactions involving Xe ions and SF ₆ ⁻ and SF ₅ ⁻ molecular ions. Zh. Tekh. Fiz. 68, 36–42 (February 1998)     

Free electron in compressed inert gases

The behavior of excess and intrinsic free electrons inside compressed inert gases is described as a function of pressure by using a pairwise approximation for the electron interaction with atomic surroundings. The change of sign from negative to positive for the xenon atom electric potential inside condensed xenon is predicted to occur at a pressure around 3 GPa, preventing slow electron embedding into solid xenon from the gas phase at higher pressure. To overcome this difficulty, the electrons should be injected into a solid sample just before its pulsed shock loading. The ionization of xenon by pressure and its further metallization are described by decreasing the forbidden gap at the expense of increasing the xenon ground electronic term and simultaneous splitting of the upper ionized electronic state. A good coincidence between the calculated and measured pressure of the dielectric-metal transition in xenon is demonstrated. The text was submitted by the authors in English.     

129Xe and131Xe NMR of xenon on silica surfaces at 77 K

Little is known about¹²⁹Xe NMR spectral features and spin-lattice relaxation behavior, and the dynamics of xenon atoms, for xenon adsorbed on solid surfaces at cryogenic temperatures (≤77 K), where exchange with gas-phase atoms is not a significant complication. We report¹²⁹Xe NMR experiments at 9,4 T that provide such information for xenon adsorbed onto the hydroxylated surface of a number of microporous silica samples at 77 K. A convenient design for these cryogenic experiments is described. Dynamics of surface-adsorbed xenon atoms on the time scale of seconds can be observed by¹²⁹Xe NMR hole-burning experiments; much slower dynamics occurring over hours and days are evidenced from changes with time of the¹²⁹Xe NMR chemical shifts. The peak maxima occur in the region ca. 180–316 ppm, considerably downfield of¹²⁹Xe shifts previously reported on surfaces at higher temperatures, and closer to the shift of xenon bulk solid (316.4±1 ppm). The¹²⁹Xe spin-lattice relaxation timesT ₁ range over five orders of magnitude; possible explanations for both nonexponential relaxation behavior and extremely shortT ₁ values (35 ms) are discussed. Preliminary¹³¹Xe and¹H NMR results are presented, as well as a method for greatly increasing the sensitivity of¹²⁹Xe NMR detection at low temperatures by using closely-spaced trains of rf pulses.     

Monte carlo simulations of low-energy (<10eV) electron transmission and reflection experiments: application to solid xenon

A Monte Carlo method is developed for simulating low-energy (< 10 eV) electron-impact transmission and reflection experiments. This method is applied to test the results obtained with various electron transport models which have recently been proposed for the interpretation of these experiments on thin solid xenon films. Particular attention is given to the critical examination of the adequacy of the assumption of isotropy of the collisions which is generally used in these models to calculate the various electron transport parameters, such as the elastic and inelastic electron scattering mean free paths. The simulation is also used to predict both the variation of the electron current transmitted through the films with the incident angle of the electron beam and the angular distribution of the reflected electrons.     

A proposed ablation laser

A new type of eximer laser is proposed; it involves the simultaneous sublimation and excitation of a frozen film by means of a relativistic electron beam. Calculated beam requirements for noble gases are ～ 10 kA/cm² of 400 kV electrons for periods of 2 to 12 ns. Predicted advantages of this laser are high gain and the elimination of wavelength limiting optical windows. Preliminary experimental fluorescence spectra have been obtained from xenon films. The emission from the solid phase consists primarily of two 100 Å wide bands centered at 1690 Å and 1730 Å the fluorescence lifetimes are 4 ± 2 ns for both bands.     

Spodumene and garnet luminescence excited by subnanosecond electron beams

Pulsed cathodoluminescence of spodumene and yttrium-aluminum garnet crystals activated by Mn²⁺ and Nd³⁺ ions, respectively, is investigated. The luminescence was excited upon crystal irradiation by electron beams with current densities of 35 and 100 A/cm² and average electron energy of ∼ 50 keV for 0.1, 0.25, and 0.65 ns. It is demonstrated that the electron beam duration decreased to several tenth of a nanosecond does not lead to essential changes of the mechanisms of pulsed cathodoluminescence excitation and character of its spectrum, but in this case, the intensity of luminescence of the hole centers increases compared with the intracenter luminescence.     

Liquid xenon study under shock and quasi-isentropic compression

Abstract

The shock adiabat for liquid xenon in the density range of 5.2–7.9 g/cm³ and pressure range of 8–70 GPa was investigated. The brightness temperature of a shock wave front from 5000 K to ?15,000 K, as well as the electrical conductivity behind the front from 4·10³ to 1.2·10⁵ 1/Ohm m, were measured. X-ray technique was used to measure quasi-isentropic compression of liquid xenon up to ～13 g/cm³.

The equations of state for liquid and solid phases of xenon were found. Anomalous behavior of xenon at p=8.37 g/cm³ was revealed, that is due to a structural transition.     

Effects of exciton-photon interaction and spatial dispersion in xenon crystals

New data on luminescence from xenon crystals are discussed in terms of the polariton theory, and the treatment of a fine spectrum structure is proposed based on the polariton scattering with participation of some acoustic phonons.The effect of spatial dispersion on transmission and reflection spectra of solid Xe is considered. Verification of the basic parameters of polariton spectrum in xenon is made by comparing calculated and experimental data.     

Spectra of highly ionized xenon (6–30?nm) excited in W7-AS plasmas

The xenon spectrum, excited in ECR- and NBI-heated plasmas with central electron densities of around 10²⁰ m^-3, and central electron temperatures from 0.7 to 2.5 keV, has been studied photoelectrically with a multi-channel grazing-incidence spectrometer. Besides numerous well-known lines of Zn- and Cu-like Xenon, more than 50 additional lines which have not yet been published in the literature have been found and partly identified,. Received: 20 December 2000 / Published online: 8 June 2001     

Electroluminescence of the electrolyte/n-ZnSe junction under anodic polarization

The electroluminescent properties of the electrolyte/ZnSe junction give important information on electron transfer across the interface. Adsorption of OH^? groups on it, that enables electron injection into the semiconductor, accounts for a luminescence at 2.0 eV, produced by an impact-ionization mechanism already observed in solid state diodes. Addition of Cu²⁺ ions in the electrolyte gives an additional luminescene at an energy of 2.2 eV. This phenomenon is connected to the adsorption of Cu⁰ and Cu²⁺ onto the semiconductor surface in relation with a corresponding energy level Cu^X_Zn in the semiconductor bulk.     

连续氙灯发光光谱的设计与应用研究

对太阳实际光谱与连续氙灯的光谱进行了测试,结果显示氙灯发光光谱的红外部分占全部光谱的55.6%,与实际太阳光谱的28.4%有较大差别。依据这种差别进行光谱曲线拟合,得到925 nm最低点的透过率曲线。采用滤光片对氙灯发光光谱的红外部分光强进行适当过滤,测得过滤后的光谱达到标准匹配度。通过测试滤光后6个不同位置点的光谱发现,光谱最大偏差仅为12.5%,表明过滤后的氙灯光谱均匀性较好。利用电致发光检测有缺陷的硅电池进行电池的电性能测试,发现经过采用滤光片和未采用滤光片的连续氙灯光照测试的Ⅰ-Ⅴ电性能值不同,功率相差0.22 W,表明氙灯光谱匹配度直接影响电池电性能测试的准确度。     

Xenon induced changes of plasma drop and electron temperature of a thermionic converter

The I–V curves of a thermionic converter were measured for several cesium pressures and various electrode distances, and partial pressures of added xenon as well. The minimum internal voltage drop across the electrode gap was determined and correlated with cesium pressure, spacing and xenon pressure. Without xenon added this voltage drop shows the well-known minimum at an optimum pressure-spacing product ofp _Cs d=5·10⁻²cm·Torr. Only for smaller values of the pressure-spacing product the internal voltage drop can be reduced by the addition of xenon. An interpretation is achieved by a comparatively simple model assuming a uniform electron temperature in the electrode gap. Using this model, the electron temperatures were calculated for various spacings and xenon pressures. Comparing the experimental data of the internal voltage drop and the correspondingly calculated electron temperatures it turns out that, within the framework of the model used, the internal voltage drop is represented by the electron temperature. The electron temperature itself is determined by the ion balance. Presented at the 10th Intersociety Energy Conversion Engineering Conference, Newark, Delaware, USA (1975).     

Effects of composition and transparency on photo and radioluminescence of Y2O3:Eu complexes

A solid state-based method using a hot reaction chamber is applied to the synthesis of Y₂O₃:Eu particles containing Eu from 0 to 5 mol%. The produced powders are studied using X-ray diffraction (XRD), scanning electron microscopy and transmission electron microscopy (TEM), as well as photoluminescence (PL) and radioluminescence tests. TEM and XRD results revealed the powder to be mono-disperse and in the form of a solid solution. The PL of Y₂O₃:Eu powder depends on both the concentration quenching effect (due to an excess of Eu concentration) and the surface luminescence effect (depicted by a higher surface area induced by the large phosphor concentration in the solution or smaller particle sizes). A ²²Na gamma source is used to compare the recorded count rates for four Y₂O₃:Eu scintillator materials with different concentrations of Eu. Each scintillator composition is examined in four forms: solid pellets with a high volume porosity and three aqueous solutions of Y₂O₃:Eu particles of the different scintillator materials at concentrations of 25, 50 and 100 mg/mL. The radioluminescence results indicated that increasing the transparency and/or the amount of Eu mol% of the scintillators increases the net average counts.