Laser Fluorescence Method for Detection of 129I and 127I Isotopes of Molecular Iodine with the Use of Kr Laser Radiation (647.1 nm)

The absorption spectra of the ¹²⁷I₂, ¹²⁷I¹²⁹I, and ¹²⁹I₂ isotopes of molecular iodine and the spectra of fluorescence excited by radiation of a Kr laser (λ=647.1 nm) were experimentally studied and calculated. A method for simultaneous determination of the concentration of ¹²⁷I and ¹²⁹I in gas mixtures (in particular, atmospheric air) is proposed.     

氯化苯并咪唑镧的荧光光谱

对新合成的化合物氯化苯并咪唑镧HCl₄·[C₇H₆N₂(H₂O)₂]₂La及其LaCl₃·5H₂O的水溶液进行了三维荧光光谱测定,讨论了HCl₄·[C₇H₆N₂(H₂O)₂]₂La在不同波长的光激发下的荧光特性,荧光强度与浓度的关系及标题化合物的上转换荧光,即在540nm绿光的激发下可以获得紫外光(290nm)和近紫外光(360nm).     

Effective production of Xe<Subscript>2</Subscript>I excimer molecules by high-energy charged particles in Xe containing a small amount of C<Subscript>3</Subscript>F<Subscript>7</Subscript>I

An anomalously high efficiency of generating Xe₂I* excimer molecules in dense Xe–C₃F₇I gaseous mixtures with a small amount of C₃F₇I that are excited by a pulsed beam of fast electrons is discovered. The electron energy is 150 keV, and the beam current amplitude and duration are, respectively, 5 A and 5 ns. The temporal–spectral characteristics of spontaneous radiation from XeI* and Xe2I* excimer molecules are measured. Also, the luminescence times of the upper level for the B–X transition in the XeI* molecule (λ_max = 253 nm) and the upper level for the 4²Γ–1²Γ transition in the Xe₂I* molecule (λ = 352 nm), as well as the rate constants of quenching these levels by the gaseous mixture components, are determined. Based on the characteristics of the track structure of a high-energy plasma produced by charged particles in the dense gaseous medium, a model of plasma-chemical processes leading to the formation of XeI* (λ_max = 253 nm) and Xe₂I* (λ = 352 nmnm) excimer molecules in a Xe–C₃F₇I mixture with a small amount of an iodine atom donor is suggested.     

Spectroscopy of barium ions in He II

The excitation and emission spectra of Ba⁺ immersed in superfluid helium have been measured. The two absorption bands - several nm wide — are slightly blue shifted with respect to the D₁ and D₂ lines of the free ion. Three emission bands at λ₁ = 491 nm, λ₂ = 523 nm and λ₃ = 648 nm have been observed.     

基于金银合金薄膜的近红外表面等离子体共振传感器研究

利用淀积在玻璃衬底上的金银合金薄膜作为表面等离子体共振(SPR)芯片, 构建了Kretschmann结构的近红外波长检测型SPR传感器. 采用不同浓度的葡萄糖水溶液测试了金银合金薄膜SPR传感器的折射率灵敏度. 实验结果表明随着入射角从7.5°增大到 9.5°, SPR吸收峰的半高峰宽从292.8 nm 减小到 131.4 nm, 共振波长从 1215 nm蓝移到 767.7 nm, 折射率灵敏度从35648.3 nm/RIU 减小到 9363.6 nm/RIU.在相同的初始共振波长(λ_R)下获得的金银合金薄膜SPR折射率灵敏度高于纯金膜(纯金膜在λ_R=1215 nm下的折射率灵敏度为29793.9 nm/RIU). 利用1 μmol/L的牛血清蛋白(BSA)水溶液测试了传感器对蛋白质吸附的响应.结果表明, BSA分子吸附使得金银合金薄膜SPR吸收峰红移了12.1 nm而纯金膜SPR吸收峰仅红移了9.5 nm. 实验结果还表明, 在相同λ_R下, 金银合金薄膜SPR吸收峰的半高峰宽大于纯金膜的半高峰宽, 因此其光谱分辨率比纯金膜SPR传感器低. 关键词： 金银合金薄膜 表面等离子体共振 波长检测型 高灵敏度     

Nonlinear light absorption and luminescence in silicate glasses

The study of luminescence of high-purity multicomponent silicate glasses excited by radiation of a N₂ laser (λ=337 nm, P≈12kW) showed darkening of a sample and a monotone decrease in luminescence intensity and the transmitted radiation intensity from pulse to pulse. Additional illumination with radiation of an Ar⁺ laser (λ=514.5 nm) caused an increase in luminescence intensity. An increase in absorption and a decrease in luminescence intensity were found to be caused by two-photon absorption and electron-hole pair production.     

Pulsed laser treatment at Fe/C6H6 interface: A Mössbauer effect study

The pulsed ruby laser induced reactive-quenching process at Fe/C₆H₆ Ibenzenel has been investigated using conversion electron Mössbauer spectroscopy [CEMS]. It is shown that iron carbide phases can be synthesized when an iron foil immersed in benzene is treated with ruby Laser pulses [λ=694 nm, pulse width ～30 ns, energy density =15 J/cm²]. The results indicate the formation of ε-carbide and Fe₅C₂ phases in the as-treated sample and its transformation to Fe₃C upon thermal treatment. The result of the CEMS measurements are supported by small angle X-ray diffractometry.     

Identification of two Ag‐2,2′:6′,2″‐terpyridine surface species on Ag nanoparticle surfaces by excitation wavelength dependence of SERS spectra and factor analysis: evidence for chemical mechanism contribution to SERS of Ag(0)–tpy

Measurement and interpretation of the excitation wavelength dependence of surface‐enhanced Raman scattering (SERS) spectra of molecules chemisorbed on plasmonic, e.g. Ag nanoparticle (NP) surfaces, are of principal importance for revealing the charge transfer (CT) mechanism contribution to the overall SERS enhancement. SERS spectra, their excitation wavelength dependence in the 445–780‐nm range and factor analysis (FA) were used for the identification of two Ag‐2,2′:6′,2″‐terpyridine (tpy) surface species, denoted Ag⁺–tpy and Ag(0)–tpy, on Ag NPs in systems with unmodified and/or purposefully modified Ag NPs originating from hydroxylamine hydrochloride‐reduced hydrosols. Ag⁺–tpy is a spectral analogue of [Ag(tpy)]⁺ complex cation, and its SERS shows virtually no excitation wavelength dependence. By contrast, SERS of Ag(0)–tpy surface complex generated upon chloride‐induced compact aggregate formation and/or in strongly reducing ambient shows a pronounced excitation wavelength dependence attributed to a CT resonance (the chemical mechanism) contribution to the overall SERS enhancement. Both the resonance (λ_exc = 532 nm) and off‐resonance (λ_exc = 780 nm) pure‐component spectra of Ag(0)–tpy obtained by FA are largely similar to surface‐enhanced resonance Raman scattering (λ_exc = 532 nm in resonance with singlet metal to ligand CT (¹ MLCT) transition) and SERS (λ_exc = 780 nm) spectra of [Fe(tpy)₂]²⁺ complex dication. Copyright © 2014 John Wiley & Sons, Ltd.     

Laser synthesis of semiconductor nanostructures with narrow band gap

Semiconductor nanostructures with narrow band gap were synthesized by means of laser chemical vapor deposition (LCVD) of elements from iron carbonyl vapors [Fe(CO)₅] under the action of Ar⁺ laser radiation (λ_L = 488 nm) on the Si substrate surface. The temperature dependence of the specific conductivity of these nanostructures in the form of thin films demonstrated typical semiconductor tendency and gave the possibility to calculate the band gap for intrinsic conductivity (E_g) and the band gap assigned for impurities (E_i), which were depended upon film thickness and applied electrical field. Analysis of deposited films with scanning electron microscopy (SEM) and atomic force microscopy (AFM) demonstrated their cluster structure with average size not more than 100 nm. Semiconductor properties of deposited nanostructures were stipulated with iron oxides in different oxidized phases according to X-ray photoelectron spectroscopy (XPS) analysis.These deposited nanostructures were irradiated with Q-switched YAG laser (λ_L = 1064 nm) at power density about 6 × 10⁷ W/cm². This irradiation resulted in the crystallization process of deposited films on the Si substrate surface. The crystallization process resulted in the synthesis of iron carbide-silicide (FeSi_2−xC_x) layer with semiconductor properties too. The width of the band gap E_g of the synthesized layer of iron carbide-silicide was less than for deposited films based on iron oxides Fe₂O_3−x (0 ≤ x ≤ 1).     

Emission spectra of iron doped ZnSxSe1-x solid solutions

The photoluminescence of ZnS_xSe_1?x:Fe has been investigated in the visible and near infrared (λ ? 1.2 μm) region. The doping dependence shows, that the incorporation of iron in ZnS produces, in addition to the well-known red luminescence (λ_max = 660 nm), another emission band at 980 nm, which was hitherto unknown for ZnS: Fe. The energetic position of this new band is proved to be independent of composition of the ZnS_xSe_1?x solid solution. Therefore, it is interpreted as an internal transition in iron centres. On the other hand, the red Fe-band shifts to lower energy with increasing selenium concentration. This result shows clearly, that the red Fe-band of zincsulfide cannot be interpreted by an internal transition in iron centres [3], but favors the donor-acceptor model, which was already suggested by other authors [4].     

Measurement of the decay-probability of metastable hydrogen by two-photon emission

The two-photon-decay probability of the metastable 2² S_{$\text{1}\text{2}$} level of hydrogen has been measured. The result A(λ)dλ = 1.5 sec^?1 ± 43% in the spectral range dλ = (255.4?232)nm ± 5% is in agreement with the theoretical prediction.     

Persistent Luminescence of Eu2☎ and Na☎ Doped Alkaline Earth Aluminates

The luminescence and afterglow properties of the Eu^2? and Na^? doped alkaline earth aluminales, stoichiometric and non-stoichiometric (M_x Al₂O₄:Eu^2?, Na^?; M = Ca or Sr, x = 0.97, 1.00 or 1.03, X_Na, = 0.02), were studied. Broad band luminescence and afterglow of the Eu^2? ion were observed in the blue (λ_max = 440nm) and green (λ_max = 520nm) region for the calcium and strontium aluminates, respectively. Both Na^? co-doping and strontium excess quenched the afterglow efficiently. The results supported the mechanism of the persistent luminescence where the cation vacancies act as traps. The results for the calcium aluminates were ambiguous, probably due to the slightly larger ionic radius of the Na^? with respect to that of Ca^2?. The sodium ions may not fit into the calcium sites and thus form (an) independent compound(s).     

Dependence of the cesium absorption D1 linewidth on the thickness of atomic vapor column

A new nanocell has been elaborated, where the thickness of the atomic vapor column varies smoothly in the range L = 350–5100 nm. The cell allows studying the behavior of the resonance absorption at the D₁ line of cesium atoms by varying the thickness from L = λ / 2 to L = 5 λ with the step λ / 2 (λ being the resonant wavelength of the laser, 894 nm) and the laser intensity. It is shown that at low laser intensities a narrowing of the resonance absorption spectrum is observed for L = (2n + 1)λ/2 (with an integer n) up to L = (7/2)λ, whereas for L = nλ the spectrum broadens. The developed theoretical model well describes the experiment.     

Synthesis and luminescence properties of mesophase silica thin films doped with in-situ formed europium complex

Mesophase silica thin film doped with in-situ formed ternary Eu complex was synthesized by adding ligands (DBM=dibenzoylmethane, phen=1,10-phenanthroline), Eu ions (EuCl₃·6H₂O), and Pluronic P123 triblock copolymer into hydrolyzed tetramethoxy-silane (TMOS). The structure of this inorganic/organic film was characterized as a 2d-hexagonal structure by X-ray diffraction (XRD) and TEM analysis. The excitation spectra (λ_em=612 nm) and emission spectra (λ_ex=325 nm) indicated that the ternary complex, Eu-DBM-phen, was formed in-situ during the formation of the film. The mesophase silica thin film doped with the in-situ formed Eu complex showed a higher quantum efficiency compared to a pure Eu(DBM)₃phen complex and a mesophase silica thin film doped with in-situ formed binary Eu-phen complex.     

Transformation of Bessel Beams in <Emphasis Type="Italic">C</Emphasis>-Cuts of Uniaxial Crystals by Varying the Emission Source Wavelength

We investigate experimentally the transformation of zero-order Bessel beams to a second-order Bessel eam in a c-cut of a CaCO₃ crystal. We show that the output-beam shape can be controlled by varying the emission-source wavelength and using a diffractive axicon. Beams were converted nearly totally at a wavelength change of Δλ = 1.5 nm and an initial wavelength λ = 637.5 nm of a CaCO₃ crystal, 15 mm in length, and a diffractive axicon with a period of 2 μm. We estimate the required wavelength variation Δλ = 1.7 nm, which is consistent with the experimental results.     

Photochemical preparation of nitrosomethanol: Vibrational frequencies,force field,and normal coordinate analysis of the cis and trans isomers

The previously unknown molecule C-nitrosomethanol [H₂C(OH)(NO)] and seven of its isotopic modification [¹³C, ¹⁸OH, ¹⁵N, D₃, D₃-¹⁵N, H₂C(OD)(NO), and HDC(OH)(NO)] have been photolytically prepared from the corresponding methylnitrite isotopes in a low-temperature argon matrix. By irradiating methylnitrite into its $\text{S}{}_1\text{(nπ}{}^1\text{← S}{}_0$ transition at 365 nm, the molecule is transformed into a hydrogen-bonded 1:1 complex between formaldehyde and nitroxyl. Photolysis of this complex produces either the trans (λ_exc = 345 nm) or the cis (λ_exc ≥ 645 nm) isomer of nitrosomethanol. Selective photoisomerization processes permit interconversion of the conformers (cis → trans with λ_exc = 510 nm and trans → cis with λ_exc ≥ 645 nm). The ir spectra (40–170 cm^?1) of cis- and trans-nitrosomethanol were measured and analyzed in conjunction with a normal coordinate analysis based on a constrained valence force field (transferable valence force field approach). The frequencies of cis- and trans-nitrosomethanol were assigned and their force fields determined.     

Interaction between localized and propagating surface plasmons: Ag fine particles on Al surface

Samples consisting of Ag fine particles 4nm in size placed near to an Al surface were prepared by depositing Ag-SiO₂ composite films by a rf cosputtering method onto vacuum-evaporated Al films. Angle-scan attenuated total reflection (ATR) measurements were performed over a wide wavelength range (λ=350-630nm) covering the resonance region (λ-410nm) of localized surface plasmon (LSP) in the Ag particles. It was found that the existence of Ag fine particles near to the Al surface led to a deformation of the dispersion curve of the surface plasmon polariton (SPP) propagating on the Al surface, in particular, in the LSP resonance region. The interaction between LSP and SPP was found to become much stronger as the distance between the particles and the surface decreases. The theoretical calculations based on the effective medium theory, which gave an effective dielectric function of the Ag-SiO₂ composite film, reproduced the deformation of the dispersion curve of the SPP. The deformation of the dispersion observed experimentally was qualitatively explained by the behavior of the effective dielectric function of the Ag-SiO₂ composite film.     

Tunable XUV radiation generated by nonresonant frequency tripling in neon

Nonresonant frequency tripling of ultraviolet (UV) radiation (λ_uv = 216–223 nm, generated by sum frequency mixing of the outputs of a frequency doubled pulsed dye laser and of the Nd-YAG pump laser) generates in neon coherent light in the extreme ultraviolet (XUV). The XUV radiation is tunable in spectral regions of negative dispersion λ_xuv = 72.05- 73.58 nm and λ_xuv = 74.3–74.36 nm at the high energy side of the transitions $\text{2p-3s′[}\text{built1}\text{2}\text{, 1]}$ and $\text{2p-3s[}\text{built3}\text{2}\text{, 1]}$. At UV input powers of 0.1-0.3 MW the generated XUV power was typically P_xuv = 0.1-0.4 W (1.5–6 x 10⁸ photons/pulse). Since present UV dye laser systems provide at λ_uv pulse powers of almost 1 MW the XUV output could easily be increased by more than one order of magnitude.     

Absorption by XeCl* excimer molecules of their own emission of the В–Х transition (λ = 308 nm) in a dense Ar–Xe–CCl<Subscript>4</Subscript> medium upon pumping by fast electrons and uranium-235 fission fragments

Luminescence of dense Ar–Xe–CCl₄ gas mixtures with a low CCl₄ content upon pumping by fast electrons and uranium-235 fission fragments is studied by spectroscopic methods. It is found that, in a cell with a resonator tuned to the В–Х transition of the XeCl* molecule (λ = 308 nm), the D-state population of the XeCl* excimer molecule (the D–X transition, λ = 235 nm) depends on the B-state population and increases by many times with increasing B-state population of the XeCl* molecule. The stimulated absorption coefficient k = 1.2 × 10^–16 of В–Х transition emission of the XeCl* molecule (λ_max = 308 nm), which leads to population of the D-state of this molecule, and the coefficient of amplification μ = 2.5 × 10^–4 cm^–1 of В–Х transition emission of the ХеCl* molecule (λ = 308 nm) are measured upon pumping by uranium- 235 fission fragments with the specific energy input into the gas medium of ~60 mJ/cm³ and a specific power of energy input of about 240 W/cm³.     

Magnetic and Structural Properties of the Mechanically Alloyed Nd2(Fe100 − x Nb x )14B System

In this work we report the magnetic and structural properties obtained by Mössbauer spectrometry, Vibrating Sample Magnetometer and X-ray diffraction of milled powders with initial composition Nd₂(Fe_{100 ? x} Nb _x )₁₄B with x = 0 and x = 4. The mixtures were ball milled for different times up to 240 h. Structural and microstructural parameters were derived from high statistics X-ray patterns and discussed as a function of milling time. The Mössbauer spectra of the samples were fitted by means of a sextet and an hyperfine field distribution, associated to a pure iron phase (α-Fe) and a disordered iron-based phase, respectively. The α-Fe grain size decreases from 50 nm for 6 h up to 5 nm for 240 h milling time. The Vibrating Sample Magnetometer results allow to conclude that these samples behave as soft ferromagnets.