Soft X-ray amplification by Li-like Al10+ and Si11+ ions in recombining plasmas

Experimental studies of soft X-ray lasers were carried out on the six-beam laser facility and the LF 12 laser facility of SIOM. Using a home-made one-dimensional spatially resolved grazing incidence grating spectrograph, XUV amplification has been observed in Li-like aluminum and silicon ions, by irradiation of slab targets with a line-focused laser. Based on time-integrated measurement, gain coefficients are 3.1 cm^–1 for the 105.7 Å 5f–3d transition in Li-like Al ions, and 1.5 cm^–1 and 1.4 cm^–1 for the 88.9 Å 5f–3d and the 87.3 Å 5d–3p transitions in Li-like Si ions, respectively. The maximum gain × length products (GL) are about 2.5.     

Conditions for XUV amplification considering recombination in clusters

3 cm^-l for a wavelength of λ_R≈200 Å in a time ≲1 ps can be expected. The measurable gain G_real depends on the cluster density N_cl. For N_cl≈10¹⁶ cm^-3 we expect G_real≳20 cm^-1. Received: 30 October 1997     

MeV Al+ and Al2+ ions implantation in Si(100): surface roughness and defects in the bulk

This paper deals with the implantation of high-energy (1.0–3.0 MeV) atomic and molecular Al⁺ ions in Si(100) to a fluence of 5×10¹⁴ Al atoms/cm² at room temperature. The molecular effect, i.e. the increase of the displacement yield compared with the sum of the atomic yields, and the damage formation as well as defect behaviour after annealing have been investigated. A detailed experimental study has been made of the evolution of extended secondary defects which form during thermal anneals of Al⁺ or Al₂ ⁺ irradiated silicon. The samples have been examined using combined Rutherford backscattering and channeling experiments together with transmission electron microscopy observations. The surface structure of the implanted wafers has been measured by atomic force microscopy. The results for the implantation-induced roughness at the Si surface, resulting from Al⁺ or Al₂ ⁺ irradiation at the same energy/atom, total atomic fluence, flux rate, and irradiation temperature, are presented and discussed. Received: 19 August 1999 / Accepted: 20 October 1999 / Published online: 23 February 2000     

Luminescent properties of Eu2+and Dy3+ ions in Ba4Al2O7 phosphor for solid state lighting

In this paper we report the combustion synthesis of rare earth (RE=Eu, Dy) doped Ba₄Al₂O₇ phosphors. Prepared phosphors were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), CIE color co-ordinates and their photoluminescence (PL) properties were also investigated. In case of Ba₄Al₂O₇: Eu²⁺, the emission spectra show unique band centered at 495 nm, which corresponds to the 4f⁶5d¹→4f⁷ transition of Eu²⁺, and PL emission spectra of Dy³⁺ ion under 348 nm excitation give two bands centered at 478 nm (blue) and 575 nm (yellow), which originate from the transitions of ⁴F_9/2→⁶H_15/2 and ⁴F_9/2→⁶H_13/2 of Dy³⁺, respectively. The results indicate that the Eu²⁺ and Dy³⁺ activated Ba₄Al₂O₇ phosphor could find application in solid state lighting.     

Intensity parameters for Er<Superscript>3+</Superscript> ions in calcium-niobium-gallium garnet crystals

Based on the analysis of the absorption spectra of Er-doped calcium-niobium-gallium garnet (Er:CNGG) crystals according to the Judd-Ofelt theory, the intensity parameters for these crystals are determined to be Θ₂ = 3.43 × 10^?20 cm² Θ₄ = 1.20 × 10^?20 cm², and Θ₆ = 0.58 × 10^?20 cm². The parameters found are compared with the intensity parameters for other laser oxide crystals. Using these intensity parameters, the probabilities of radiative transitions between the energy levels of Er³⁺ ions in CNGG crystals and the luminescence branching ratios β_JJ’ are calculated. From the measured lifetime of the ⁴ I _11/2 level of Er³⁺ ions (τ = 626 μs) and the probability of the radiative transition from this level (A = 192 s^?1), it is found that about 88% of the excitation energy in the Er:CNGG crystals is nonradiatively transferred from the ⁴ I _11/2 to the ⁴ I _13/2 level. It is suggested that an increase in the oscillator strength and in the line strength of the ⁴ I _15/2 → ² H _11/2 transition of Er³⁺ in CNGG crystals, as well as an increase in the intensity parameter Θ₂ with respect to the corresponding parameters for other garnet crystals are caused by the existence in CNGG crystals of Er³⁺ centers with the environment symmetry lower than D ₂.     

Low‐dose ion implanted active waveguides in Nd3+ doped near‐stoichiometric lithium niobate: promising candidates for near infrared integrated laser

By applying low‐dose oxygen ion implantation, active planar waveguides in Nd³⁺ doped near‐stoichiometric lithium niobate laser crystals have been, for the first time to our knowledge, successfully produced. The waveguide exhibits good transmission properties with relatively low propagation loss of ～2 dB/cm. The confocal micro‐luminescence investigations indicate that the emission properties of Nd³⁺ ions in the waveguide are well preserved with respect to the bulk, thus showing promising potentials for efficient waveguide laser action operating at the Nd³⁺ near‐infrared bands. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effective excitation cross section and lifetime of Er<Superscript>3+</Superscript> ions in Si: Er light-emitting diodes fabricated by sublimation molecular-beam epitaxy

A series of Si: Er electroluminescent diode structures is fabricated by sublimation molecular-beam epitaxy. The diode structures efficiently emit at a wavelength of 1.5 μm under conditions of p-n junction breakdown at room temperature. The effective cross section of excitation of Er³⁺ ions with hot carriers heated by the electric field of a reverse-biased p-n junction and the lifetime of Er³⁺ ions in the first excited state ⁴I_13/2 are determined for structures that emit in a mixed breakdown mode and are characterized by the maximum intensity and excitation efficiency of the Er³⁺ electroluminescence.     

Eu^3＋离子在晶体KY3F10,YPO4及YVO4中的角重迭晶场参数计算

本文运用角重迭模型首次对Eu~(3+)离子在KY_3F_(10)S、YPO_4及YVO_4晶体中的四个角重迭参数e_σ、e_π、e_δ、e_φ进行了计算。结果表明,所得规律与文献[1]基本相符,并且e_σ和e_φ两个参数对能级的劈裂和移动也有着不可忽略的作用。     

The magnetic moment of the 10+ isomer in140Ce and temperature dependence of the paramagnetism for Ce ions in BaO

The g-factor of the first 10⁺ isomer in¹⁴⁰Ce was determined by the time differential perturbed angular distribution method. The result is g(10⁺) = +1.03(4). The paramagnetism of Ce ions in BaO was studied in the temperature region 300 – 850 K.     

Nitrogen-doped carbon dots embedded in a SiO<Subscript>2</Subscript> monolith for solid-state fluorescent detection of Cu<Superscript>2+</Superscript> ions

We describe the simple fabrication of SiO₂ sol-gel monoliths embedding highly luminescent carbon nanodots (CDs) sensitive to metal ions. The pristine CDs we synthesize display an intense dual emission consisting in two fluorescence bands in the green and violet region, and we demonstrate that this photoluminescence is substantially unchanged when the dots are incorporated in the SiO₂ matrix. The emission of these CDs is quenched by interactions with Cu²⁺ ions, which can be used to detect these ions with a detection limit of 1 μM. The chromophores remain accessible to diffusing Cu²⁺ ions even after embedding CDs in the sol-gel monolith, where their detection capabilities are preserved. Such a result provides the proof-of-principle of a new sensing scheme, where CDs are exploited as active sensing centers of metal transition ions within a solid-state device. The different interaction mechanisms of CDs with copper, in liquid and solid phase, are analyzed in detail and discussed in terms of different accessibility of their chromophores when the dots are incorporated in the SiO₂ matrix.     

Zero-field splitting and local structure for V<Superscript>2+</Superscript> ions in CsMg<Emphasis Type="Italic">X</Emphasis><Subscript>3</Subscript> (<Emphasis Type="Italic">X</Emphasis>=Cl,Br, I) crystals

The zero-field splitting and local structure for V²⁺ ions in CsMgX ₃ (X =Cl, Br, I) crystals are theoretically investigated using complete diagonalization method (CDM) for a 3d ³ ion in trigonal symmetry. Spin-spin (SS) and spin-other-orbit (SOO) interactions are taken into account in addition to the general spin-orbit (SO) interaction. On this basis, using ligand ion displacement model, we find that the ligand ions move away from C ₃-axis, and therefore the local angles in the V²⁺ centres are larger than the angles in the hosts. The results show good agreement with the observed values.     

Raman spectroscopic study of the hydrogen and arsenate bonding environment in isostructural synthetic arsenates of the variscite group—M3+ AsO4·2H2O (M3+ = Fe,Al, In and Ga): implications for arsenic release in water

The Raman spectra of synthetic compounds equivalent to the variscite group: FeAsO₄·2H₂O AlAsO₄·2H₂O, GaAsO₄·2H₂O, and InAsO₄·2H₂O are reported. In particular, upon comparison of FeAsO₄·2H₂O to AlAsO₄·2H₂O, it is observed that the Type II (weak) H‐bond lengths in the latter are slightly longer, which is postulated to affect the stability (As release) in water at pH 5 and 7. Arsenate stretching and bending vibrations were found to be distinct in terms of spectral structure and therefore well suited for fingerprinting. The calculated As O bond strengths from existing crystallographic data showed no significant variations. The strongest ν₁ (AsO₄³⁻) stretch was used to monitor the As O bonding interactions in the four As O M units, where a shift of 114 cm⁻¹ was observed in the order FeAsO₄·2H₂O (lowest) < InAsO₄·2H₂O < GaAsO₄·2H₂O < AlAsO₄·2H₂O (highest); this order also followed exactly the measured arsenic release of these phases. This shift in ν₁ (AsO₄³⁻) position was rationalized to stem from the differences in the electronegativities of the M³⁺ cations. The trends mentioned above were verified and found to also hold for the isostructural phosphate analogues strengite (FePO₄·2H₂O) and variscite (AlPO₄·2H₂O) using published data. Therefore, it is postulated that, as observed with the stability of solution complexes, there may be a correlation between the electronegativity of the M³⁺ cation in these isostructural phases and their stability (As or P release) in water. Copyright © 2010 John Wiley & Sons, Ltd.     

Electrochemical behaviour of nano-sized spinel LiMn2O4 and LiAlxMn2−xO4 (x=Al: 0.00-0.40) synthesized via fumaric acid-assisted sol-gel synthesis for use in lithium rechargeable batteries

Pristine spinel LiMn₂O₄ and LiAl_xMn_2−xO₄ (x=Al: 0.00-0.40) with sub-micron sized particles have been synthesized using fumaric acid as chelating agent by sol-gel method. The synthesized samples were subjected to thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and cyclic voltammetry (CV) and galvanostatic cycling studies. The TGA curve of the gel shows several weight-loss regions stepwise amounting to 55% till 800 °C attributed to the decomposition of the precursors. Calcination to higher temperatures (800 °C) yields pure-phase spinel (LiAl_xMn_2−xO₄), as it is evident from the high-intensity XRD reflections matching to the standard pattern. SEM and TEM studies confirm that the synthesized grains are of uniform regular surface morphology. FT-IR studies show stretching and bending vibration bands of Li-O, Li-Al-Mn-O. LiAl_0.1Mn_1.90O₄ spinel was found to deliver discharge capacity of 139 mA h/g during the first cycle with columbic efficiency of 97%. LiAl_0.1Mn_1.90O₄ spinel exhibits the high cathodic peak current indicating better electrochemical performance. Low doping (x=0.1) of Al is found to be beneficial in stabilizing the spinel structure.     

Hg~+离子5d~(10)6s ~2S_(1/2)→5d~96s~2 ~2D_(5/2)钟跃迁同位素位移和超精细结构的理论研究

本文首先在Dirac-Hartree-Fock近似下理论评估了Hg~+离子5d~(10)6s ~2S_(1/2)→5d~96s~2 ~2D_(5/2)钟跃迁的质量位移(mass shift, MS)和场位移(field shift, FS)在其同位素位移(isotope shift, IS)中的相对贡献,发现MS远小于FS而可以被忽略.在此基础上,通过系统地考虑该原子体系中主要的电子关联效应,计算了这条钟跃迁FS的精确值以及涉及到的上下两个能级的超精细结构常数,并得到了几种稳定汞同位素离子该跃迁的IS和超精细结构分裂.其中,计算的~(199)Hg~+和~(198)Hg~+离子之间的钟跃迁频率偏移与已有实验测量值相比误差为2%左右.最终,本文给出了汞离子7种常见同位素该谱线的绝对频率值,为实验上的谱线测量提供了有效的理论依据.