Potential Energies of the Orbitally Degenerate Atmospheric Rydberg Complexes

A method was developed for calculating the vibronic potential energy surfaces (PESs) of atmospheric complexes consisting of orbitally degenerate Rydberg nitrogen and oxygen molecules and the molecules of a neutral medium in the ground electronic state. The degenerate states are formed as a result of l-mixing in the D and E layers of the atmosphere during the periods of increased solar activity. The complexes are populated in the nonequilibrium two-temperature plasma and are responsible for the incoherent additional background radiation in the decimeter (microwave) and terahertz (IR) bands at an altitude of 80–110 km from the Earth’s surface. To describe the interaction of a weakly bound electron with a singly charged molecular ion and a neutral molecule of a gas medium, the formalism of the multichannel quantum defect (MCD) theory was used. Quantum-chemical calculations of the dependences of the scattering lengths, polarizabilities, and quadrupole moments of the main atmospheric molecules N₂ and O₂ on the interatomic distance were performed. The specific features of the behavior of vibronic PESs of Rydberg complexes for large values of the principal quantum number (n ? 1) were analyzed. The vibronic PESs of orbitally degenerate states were constructed. They are necessary for determining the positions and shape of the vibronic minima of the l-mixing cross sections of the N₂ and O₂ Rydberg molecules in the D and E layers of the Earth’s atmosphere, where the delay times of satellite positioning signals should be minimum. The possibility of “quantum chaos” appearing in the Rydberg complexes at sufficiently large n values and angular momenta of the weakly bound electron was noted.     

Effect of limiting polarization in the Jovian inner magnetosphere

Jovian decameter emission is known to exhibit almost total polarization. We consider the elliptical polarization to be a consequence of linear-mode coupling in the Jovian magnetosphere outside the source region. We determine conditions of emission propagation along the ray path that are necessary for self-consistent explanatation of the polarization observations and show that the ellipticity (axial ratio of the polarization ellipse) is determined by the magnetospheric plasma density n_e in a small region a distance of about half the Jovian radius from the radiation source. The plasma density in the region is quite low, n_e<0.4 cm⁻³, and the geometrical-optics approximation of emssion propagation in front of the region converts to the vacuum approximation behind it. The latter means that the linear-mode coupling in the Jovian inner magnetosphere is manifested as the effect of limiting polarization. Sources of decameter emission emitting at different frequencies f are located at heights corresponding to gyrofrequency levels f _Be ≅f and at magnetic-force lines that belong to L-shells passing through the satellite Io. The location of the transitional region in the Jovian magnetosphere varies depending on the emission frequency and the time. For each given decameter radio emission storm occupying some region in frequencytime space, we have a number of transitional regions located in a certain region of the Jovian magnetosphere—the interaction region of the magnetosphere (IRM) for the given emission storm. The distribution of magnetospheric plasma in an IRM is found from data of observations of the polarization ellipiicity of the given decameter radio emission storm. By matching the calculated ellipticity of emission with the observed ellipticity at every point of frequency-time space of the emission dynamic spectrum one finds a recurrent relation between the local values of the magnetospheric plasma density N_c and the planetary magnetic field B in the IRM, which allows evaluation of the distribution of plasma density if a definite model of the Jovian magnetic field has been adopted. Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod, Russia; Space Research Institute, Austrian Academy of Sciences, Austria. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 2, pp. 177–193, February, 1998.     

Quasiclassical analysis of the spectra of two groups of central potentials

A method is suggested for analyzing the spectra of central attractive potentials either with Coulomb singularity (intra-atomic potentials) or finite at zero point (potentials in spherical clusters and nuclei). It is shown that, if the orbital degeneracy is removed, then $\varepsilon _{nl} - \varepsilon _{n0} \cong a_{\varepsilon _{n0} } (l + 1/2)^2 $ for small l in the shell n. In atoms and ions, the coefficient a _ε is nonnegative, so that the energy in the n shell increases with l. The validity of this formula for the inner electrons is illustrated by calculating the spectrum of the mercury atom. In cluster potentials, the opposite situation, as a rule, occurs: the larger l, the lower the corresponding level (a _ε<0). However, in the soft potentials of small clusters, spectral regions with different signs of a _ε coexist and the orbitally degenerate level exists in the spectral region where a _ε=0. Aluminum clusters Al_N are taken as an example to find out how the position of the region with the degenerate level varies with varying cluster size N, and it is found that this region is “pushed out” to higher energies with an increase in N. In this connection, the presence of multiply ionized Al_N clusters of the corresponding size in a low-temperature aluminum plasma is discussed.     

Emission of highly excited atoms and molecules in the upper atmosphere

The emission ability of Rydberg atoms and molecules in the orbitally degenerate states is considered. The mechanisms of their formation in the F, E, and D upper atmosphere layers are analyzed. The characteristic lifetimes of these states in the microwave range are estimated. It is shown that radiation in this range can be accompanied by a cascade of transitions. The possibility of studying the influence of intense atmospheric microwave radiation on living organisms is discussed.     

A double modulation technique for the detection of transient species in photoelectron spectroscopy

A technique is described to measure photoelectron spectra of transient species without the interference of signals due to parent compounds. This is achieved by modulation at the same frequency of both the microwave discharge which produces the transients and the helium UV lamp intensity, adjustment of modulation depths and relative phases, and subsequent phase-sensitive detection. As an example, part of the photoelectron spectrum of oxygen passed through a microwave discharge is presented, showing O₂ (¹Δ_g) and O atom signals in the absence of O₂ (³Σ_g^?) lines.     

Microwave and IR radiation of the upper atmosphere during periods of enhanced solar activity

A two-temperature nonequilibrium plasma in the E and D atmospheric layers at heights between 50 and 110 km during periods of enhanced solar activity is formed. The highly excited states (Rydberg states) of the A**N₂ and A**O₂ quasi-molecules are populated due to interaction with the neutral medium in the plasma. This results in propagation delays of the signals of global navigation satellite systems and in enhanced positioning uncertainties. Radiation transitions between the Rydberg states of the quasi-molecules lead to the appearance of super-background noncoherent radiation in the decimeter and infrared ranges. The decimeter radiation degrades the signal-to-noise ratio of navigation systems. The super-background infrared radiation can be used to make the tomography of the excited layer and to detect the Rydberg states.     

Radioluminescence properties of rare earths doped SrAl2O4 nanopowders

Nanopowders of SrAl₂O₄ pure and doped with rare earths were prepared via a proteic sol-gel methodology. The prepared materials presented a single crystalline phase, confirmed by XRD measurements. AFM results indicate that the average particle size is about 53 nm for SrAl₂O₄ powders. The radioluminescence spectrum of SrAl₂O₄: Eu²⁺, Dy³⁺ is composed by two intense peaks around 520 and 570 nm followed by a weaker emission peaking at 615 nm. It was observed that the intensity of RL emission during irradiation with X-rays decreased as a function of the irradiation time, indicating the build up of radiation damage in the nanopowders. The irradiated samples exhibited a persistent radiation damage that changes the colour of the sample, and also influenced the reduction in the scintillation efficiency. The saturation level of SrAl₂O₄: Eu²⁺ is 96%, exhibiting good resistance to radiation damage.     

Intrinsic photoluminescence properties of amorphous Si3B3N7 ceramic

Amorphous Si₃B₃N₇ ceramic shows intrinsic photoluminescence. Three distinctive emission regions have been observed. Excitation with wavelengths between 254 and 330 nm stimulates intense blue emissions with peak maxima ranging from 447 to 479 nm. Exciting between 315 and 420 nm results in two broad emission peaks; the first in the range between 400 and 440 nm, and the second between 560 and 690 nm. Of these two latter emissions, the one in the violet region dominates in intensity over the other one in the red region, thus a violet color is perceived with the eye via excitation with 330 nm or higher wavelengths. The three distinct intrinsic emissions in the photoluminescence spectrum of amorphous Si₃B₃N₇ ceramic are related to defect centers in three topologically different regions in its structure. Dependence of emission on excitation wavelength is associated with the Red-Edge Effect and can be explained with a reabsorption mechanism at the red excitation edge.     

The assignment of molecular infrared spectra from a laser magnetic resonance spectrometer

Mathematical techniques are presented which have proved useful in assigning the laser magnetic resonance pure-rotation spectrum of HO₂, i.e., useful in assigning an absorption spectrum obtained when molecular energy levels are Zeeman shifted by an external magnetic field until transition frequencies coincide with a fixed-frequency radiation source. The techniques described should have general applicability to the laser magnetic resonance vibration-rotation spectrum of any molecule in an orbitally nondegenerate electronic state and a doublet electronic spin state ($\text{S =}\text{1}\text{2}$). Equations involving both Zeeman line positions and Zeeman line intensities are presented. These allow the assignment of M_J quantum numbers, the determination of the spin-rotation interaction constant γ and rotational quantum number N for both the upper and the lower state, and the determination of the zero-field transition frequency. The equations can be used without prior knowledge of the molecular structure or energy levels.     

双模腔场中具有不同耦合常数的两原子多光子辐射谱

研究了与双模腔场具有不同耦合常数的两个二能级原子的多光子辐射谱,给出了双模多光子辐射谱的一般表达式.结果表明,当双模腔场分别处于不同数态时,虽然两原子与双模腔场之间具有不同的耦合常数,但对于任意的N₁和N₂(N_i(i＝1,2,)为模i腔场被每个原子吸收或发射的光子数),辐射谱总是关于共振频率ω₀对称分布;并且,当N₁＝N₂时,对于任意的数态光子数n₁和n₂交换,辐射谱不变.上述特点用解析方法给予了解释.计算了非简并双光子情况下的辐射谱,并得到了一些新结果.双模腔场中单原子及具有相同耦合常数的两原子辐射谱可从本文结果分别做为特例而得到.     

Theoretical and experimental investigation of X-ray O- and N-emission spectra of tungsten

The experimental investigation of the O_IIIN_{VI, VII}-emission spectrum of pure tungsten and tungsten in W₂C is carried out. The experimental data are compared with the theoretical calculation of the intensity in the O_IIIN_{VI, VII}-emission spectrum of tungsten. A good agreement is obtained between the theoretical and experimental spectra. The conclusion was drawn, that the earlier published experimental data on the O_IIIN_VI,VII- spectrum of tungsten referred to carbide of tungsten.     

Photoluminescence properties of Sr1-xSi2O2N2: Eux as green to yellow-emitting phosphor for blue pumped white LEDs

This study evaluated potential applications of green to yellow-emitting phosphors (Sr_1−xSi₂O₂N₂: Eu²⁺_x) in blue pumped white light emitting diodes. Sr_1-xSi₂O₂N₂: Eu²⁺_x was synthesized at different Eu²⁺ doping concentrations at 1450 °C for 5 h under a reducing nitrogen atmosphere containing 5% H₂ using a conventional solid reaction method. The X-ray diffraction patterns of the prepared phosphor (Sr_1-xSi₂O₂N₂: Eu²⁺_x) were indexed to the SrSi₂O₂N₂ phase and an unknown intermediate phase. The photoluminescence properties of these phosphors (Sr_1−xSi₂O₂N₂: Eu²⁺_x) showed that the samples were excited from the UV to visible region due to the strong crystal field splitting of the Eu²⁺ ion. The emission spectra under excitation of 450 nm showed a bright color at 545-561 nm. The emission intensity increased gradually with increasing Eu²⁺ doping concentration ratio from 0.05 to 0.15. However, the emission intensity decreased suddenly when the Eu²⁺ concentration ratio was >0.2. As the doping concentration of Eu²⁺ was increased, there was a red shift in the continuous emission peak. These results suggest that Sr_1-xSi₂O₂N₂: Eu₂⁺_x phosphor can be used in blue-pumped white light emitting diodes.     

Determination of N and O – Atom and N2(A) Metastable Molecule Densities in the Afterglows of N2 and N2‐O2 Microwave Discharges

Early afterglows of N₂ and N₂‐O₂ flowing microwave discharges are characterized by optical emission spectroscopy. The N and O atom and N₂(A) metastable molecule densities are determined by optical emission spectroscopy after calibration by NO titration for N‐atoms and measurements of NO and N₂ band intensities for O‐atoms and N₂(A) metastable molecules. By using N₂ tanks with 50 and 10 ppm impurity, it is determined in the afterglow an O‐ atom impurity of 150‐200 ppm. Variations of the N and O‐atom and N₂(A) metastable molecule densities are obtained in the early afterglow of N₂–(9·10^–5–3·10^–3)O₂ gas mixtures. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effect of annealing temperature and annealing atmosphere on the structure and optical properties of ZnO thin films on sapphire (0 0 0 1) substrates by magnetron sputtering

ZnO thin films were epitaxially grown on sapphire (0 0 0 1) substrates by radio frequency magnetron sputtering. ZnO thin films were then annealed at different temperatures in air and in various atmospheres at 800 °C, respectively. The effect of the annealing temperature and annealing atmosphere on the structure and optical properties of ZnO thin films are investigated by X-ray diffraction (XRD), atomic force microscopy (AFM), photoluminescence (PL). A strong (0 0 2) diffraction peak of all ZnO thin films shows a polycrystalline hexagonal wurtzite structure and high preferential c-axis orientation. XRD and AFM results reveal that the better structural quality, relatively smaller tensile stress, smooth, uniform of ZnO thin films were obtained when annealed at 800 °C in N₂. Room temperature PL spectrum can be divided into the UV emission and the Visible broad band emission. The UV emission can be attributed to the near band edge emission (NBE) and the Visible broad band emission can be ascribed to the deep level emissions (DLE). By analyzing our experimental results, we recommend that the deep-level emission correspond to oxygen vacancy (V_O) and interstitial oxygen (O_i). The biggest ratio of the PL intensity of UV emission to that of visible emission (I_NBE/I_DLE) is observed from ZnO thin films annealed at 800 °C in N₂. Therefore, we suggest that annealing temperature of 800 °C and annealing atmosphere of N₂ are the most suitable annealing conditions for obtaining high quality ZnO thin films with good luminescence performance.     

Determination of N and O‐atoms and N2 (A) Metastable Molecule Densities in the Afterglows of N2‐H2, Ar‐N2‐H2 and Ar‐N2‐O2 Microwave Discharges

Early afterglows of N₂‐H₂, Ar‐N₂‐H₂ and Ar‐N₂‐O₂ flowing microwave discharges are characterized by optical emission spectroscopy. The N and O atoms and the N₂ (A) metastable molecule densities are determined by optical emission spectroscopy after calibration by NO titration for N and O‐atoms and measurements of NO and N₂ band intensities. If an uncertainty of 30% is estimated on N‐atomic density, an inaccuracy of one order of magnitude is obtained on the O and N₂ (A) densities. In N₂‐(0.05‐2.5%)H₂ and Ar‐(1‐50%)N₂‐(0.05‐2.5%) H₂ gas mixtures, the O‐atoms are coming from O₂ impurities in the discharge. Concentrations of N and O‐atoms and of N₂ (A) densities are compared to the ones obtained in Ar‐(5‐50%)N₂‐(0.2‐2.5%) O₂ gas mixtures in which a controlled amount of O₂ is added. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A double ionization satellite in the tungsten Auger spectrum

The electron induced tungsten Auger spectrum exhibits a peak at 210 eV which is on the high energy side of the major Auger emissions, N_{4, 5}N_{6, 7}X (X ≡ N_{6, 7} or O_{2, 3}). The N₄N_{6, 7}V Coster-Kronig processes should occur around 210 eV but the yield curve for the 210 eV feature shows that most of the intensity arises from a process with threshold behaviour toward N₃. This process is identified as the second step in an Auger cascade: N₃ single holes decay via an N₅V state which exhibits a high probability of decaying via a particular N_{6, 7}XV three-hole state to yield electron emission at 210 eV.     

Eu$lt;sup$gt;2+$lt;/sup$gt;的掺杂浓度对BaAl$lt;sub$gt;2$lt;/sub$gt;Si$lt;sub$gt;2$lt;/sub$gt;O$lt;sub$gt;8$lt;/sub$gt;：Eu$lt;sup$gt;2+$lt;/sup$gt;荧光粉发光特性的影响

采用化学共沉淀法一次煅烧工艺合成了BaAl₂Si₂O₈：Eu²⁺蓝色荧光粉.用X射线衍射仪和荧光分光光度计等对BaAl₂Si₂O₈：Eu²⁺蓝色荧光粉的相结构、发光性能进行了测试.结果表明：化学共沉淀法一次煅烧工艺合成的BaAl₂Si₂O₈：Eu²⁺蓝色荧光粉为单相;其激发光谱分布在240—410 nm的波长范围,峰值位于320 nm处,可以被InGaN管芯产生的350—410 nm辐射有效激发;在365 nm近紫外光的激发下,测得其发射光谱是位于465 nm附近的宽带峰.BaAl₂Si₂O₈：Eu²⁺蓝色荧光粉的发光强度随Eu²⁺浓度的增大逐渐加强,当Eu²⁺掺杂的摩尔分数为3.5%时,发光强度达到最大值,而后随掺杂浓度的增加而减小,发生浓度猝灭;根据Dexter能量共振理论,该浓度猝灭是由于Eu²⁺的离子间交换相互作用引起的. 关键词： 2Si₂O₈：Eu²⁺')" href="#">BaAl₂Si₂O₈：Eu²⁺ 发光特性 蓝色荧光粉 化学共沉淀法     

Influence of the medium on the electromagnetic radiation spectrum of highly excited atoms and molecules

The influence of neutral species in the E- and D-layers of the Earth’s upper atmosphere on the spectrum of the spontaneous emission (absorption) of Rydberg atoms and molecules for transitions that occur without changing the principal quantum number (Δn = 0) is examined. Along with the process of l-mixing, the splitting of orbitally degenerate states due to interaction with perturbing neutral species of the medium is taken into account. The possible types of radiative transitions between them are analyzed. It is demonstrated that, for principal quantum numbers of n = 10–30, decimeter-band radiation corresponds to transitions between the levels of split states, whereas meter-band radiation, to transitions between their individual components. It is established that, for these values of n, the ratios of the intensities of the decimeter and meter bands for Δn = 0 transitions to the intensity of IR radiation (Δn = 1) are 10⁻⁴ and 10⁻⁶, respectively. The issue of satellite signal phase shift because of multiple Raman scattering in the D-layer of the atmosphere is discussed.     

The ultraviolet luminescence of β-galliumsesquioxide

The luminescence of β-Ga₂O₃ crystals and powder specimens has been studied in the temperature range 5–300 K. The measurements have been performed on nominally pure samples and on samples that had been doped with aliovalent cations. In all samples an emission is observed at low temperatures in the ultraviolet (UV) region of the spectrum. We conclude that this emission is intrinsic, since neither its intensity nor its position was influenced by the impurity content or the history of the samples. Measurements of the optical density and the photoconductivity in the energy range where this UV emission can be excited reveal that the UV emission is excited in an interband transition. By analogy with the well-known instrinsic emission of the alkali halides, the intrinsic UV emission in β-Ga₂O₃ is attributed to the recombination of an electron (hole) and a self-trapped hole (electron).     

Semiclassical spectrum of the two-dimensional non-linear σ models

The spectrum of O(N) invariant two-dimensional non-linear σ models is analyzed for large N by the methods of Dashen, Hasslacher and Neveu. Calculations to $\text{O}\text{(}\text{1}\text{N}\text{)}$ are carried out and the spectrum is shown to consist solely of N degenerate massive mesons. This is consistent with strong coupling lattice calculations and indicates that for sufficiently large N there is no phase transition between the weak and strong coupling regions.