Formation Dynamics of Absorbing Layers in a Two‐Stage Atomizer

An experimental spatialresolution facility for recording the formation dynamics of absorbing layers in a twostage atomizer is described. An optical scheme with a convergent raying beam in the atomizer zone and a hollow cathode as a radiation source is considered. The dynamics of the absorptivity signal at evaporation of Rb, NaCl, and a standard sample CASS2 has been investigated under different operating conditions of the atomizer. It is shown that the proposed evaporation–condensation–atomization regime considerably lowers the spatial gradients of absorptivity and the level of nonselective absorption in recording the atomic absorption signal.     

Interaction of Alkali Blue 6B with Cetyltrimethylammonium Bromide

The microsurface adsorption–spectral correction (MSASC) technique has been applied to investigate the interaction of alkali blue 6B (AB6B) with cetyltrimethylammonium bromide (CTAB). The aggregation of AB6B on CTAB obeys the Langmuir isothermal adsorption. The aggregate was characterized by MSASC. For the monomer aggregate AB6B₂CTAB formed, its binding constant is calculated to be K = 3.01·10⁵ and its molar absorptivity to be 2.45·10⁶ liters·cm^–1 at = 690 nm. The adsorption has been used to carry out quantitative detection of cationic surfactant in samples.     

Potassium Sensing by Using a Newly Synthesized Squaraine Dye in Sol-Gel Matrix

Squaraines are a group of fluorescent dyes and pigments derived from squaric acid and dialkylanilines well known in applications such as photoreceptors, organic solar cells, optical recording media, and non-linear optics. Their very promising spectral properties, long wavelength absorption and emission, and high absorptivity and quantum yields have not been exploited so far in relation to optical sensor design. They exhibit excellent solubility in sol-gel matrices, and the ligand is an integral part of the fluorophore system, which makes the molecule a fluoroionophore. In this work, potassium-sensing agent, bis[4-N-(1-aza-4,7,10,13,16-pentaox acyclooctadecyl)-3,5-dihydroxyphenyl] squaraine has been used for potassium sensing in a sol-gel matrix. The spectrofluorimetric response of dye-doped tetraethyl ortosilicate (TEOS) film after exposure to certain concentrations of K⁺ has been investigated, and 62% of relative signal change was achieved. The dynamic working range of the sensor membrane has been found between 10^–9 and 10^–6 M K⁺, in other terms from nanomolar to micromolar levels, which is an advantage over flame emission spectroscopy, in view of detection limit. The sensor is fully reversible within the dynamic range and the response time (₉₀) is found to be 2 min under batch conditions. The cross-sensitivity of the molecule to Na⁺, Ba²⁺, Ca²⁺, and NH⁺ ₄ was also tested in separate solutions.     

A frequency doubled chemical oxygen iodine laser

The output of a chemical oxygen iodine laser (=1.315 m) has been frequency doubled at an overall conversion efficiency of 1%. A lithium iodate (LiIO₃) crystal was used in an intracavity doubling scheme. This represents the first time visible laser light has been obtained, solely from a chemical source.To whom the correspondence should be addressed.     

Infrared photoluminescence of erbium-tris(8-hydroxyquinoline) in a distributed feedback cavity

A distributed feedback (DFB) waveguide cavity with erbium-tris(8-hydroxyquinoline) has been fabricated by X-ray interference lithography in a laboratory-scale apparatus. The DFB cavity consists of a large area () one-dimensional grating of polymethylmethacrylate on Si (1 0 0). Structural, morphological and optical properties of the device have been studied. On-grating narrowing of the photoluminescence emission has been observed for the 492 nm grating period in correspondence to the 4f-4f Er band peak (at 1530 nm), indicating the possibility of optical gain for applications in the telecommunications.     

Thermoregulation and spectral selectivity of the tropical butterfly Prepona meander: a remarkable example of temperature auto-regulation

In butterflies favouring direct absorption of solar energy through their wings, the absorption by the black areas situated at the wing bases provides the body with the most part of the exogenous energy. For the studied butterfly (Archeoprepona meander), absorption is very high over the whole solar spectrum (0.95). This absorption is due to both the dendritic structure of the scales and the melanin pigments. In the infrared range, the absorptivity reveals two strong peaks at 3 m and 6 m and then remains more or less constant at a relatively high value (0.4) up to 25 m. This situation contains the outline for a remarkable self-regulation phenomenon of the radiative balance, allowing the stabilization of temperature in the survival area of the butterfly. The first absorption peak, centred on 3 m, i.e. between the solar irradiance and the thermal emission spectra, is not involved in the radiative balance at these temperatures. However, the second, on the edge of the emission spectrum, plays a key role as a thermal regulator. Its marginal situation is such that, according to the wing temperature, it overlaps or not the emission spectrum, modifying the collector efficiency, and thus the temperature. PACS 44.40.+a; 78.20.Ci; 78.40.-q     

NaCl islands decorated with 2D or 3D 3,4,9,10-perylene-tetracarboxylic-dianhydride nanostructures

The formation of PTCDA (3,4,9,10-perylene-tetracarboxylic-dianhydride) nanostrutures on Au(1 1 1)-() covered with NaCl islands has been studied using scanning tunneling microscopy (STM). Atomically resolved STM images show that NaCl grows as (1 0 0)-terminated layers on Au(1 1 1)-(). Local atomic hexagonal packing has also been observed in the NaCl(1 0 0) layer. At submonolayer NaCl coverage, PTCDA forms two-dimensional islands on the Au(1 1 1) surface and nucleate preferentially at the NaCl island step edges. When the Au surface is fully covered with NaCl layers, PTCDA molecules form three-dimensional molecular clusters decorating the step edges of NaCl layers.     

Two-magnon bound states in a system of coupled electronic and nuclear spins

Two-particle complexes in ferromagnets with hyperfine electronic-nuclear coupling have been studied. The secular equation has been obtained and analysed (with numerical methods as well) in the middle and in the end of the Brillouin zone for 1- and 3-dimensional lattices (of s.c. structure). The existence of new types of complexes (nuclear-nuclear and electronic-nuclear) in strongly anisotropic systems has been established.     

Energy of the 5− isomer and (πg 9/2⊗vg 9/2) states in82Rb

Excited states in the doubly-odd nucleus⁸²Rb have been investigated via the reactions⁷⁹Br(,n) and⁷⁸Se(⁷Li,3n) using in-beam-ray spectroscopy. The level energy of the longlived 5^– isomer has been determined to 68.3 keV which is below the energy of the 2^– state found at 88.9 keV with a lifetime of=2.4(2) ns. A sequence of positive-parity states beginning with a 6⁺ level at 191.3 keV (=20(3) ns) and extending to a (10⁺) level has been interpreted to contain the two-particle configuration (g ₉/2 _9/2) and collective excitations.     

Epitaxial growth of Nd2Hf2O7(1 1 1) thin films on Ge(1 1 1) substrates by pulsed laser deposition

Nd₂Hf₂O₇ (NHO) thin films have been epitaxially grown by pulsed laser deposition (PLD) on Ge(1 1 1) substrates. In situ reflection high-energy electron diffraction (RHEED) evolution of the (1 1 1)-oriented NHO during the deposition has been investigated and shows that the epilayer has a twin-free character with type-B stacking. Interfacial structure of NHO/Ge has been examined by high-resolution transmission electron microscopy (HRTEM). The results indicate a highly crystalline film with a very thin interface, and the orientation relationship between NHO and Ge can be denoted as (1 1 1)_NHO//(1 1 1)_Ge and . Finally, twin-free epitaxial growth of NHO with type-B orientation displays temperature dependence and the type-B epitaxy is favored at high temperature.     

Focussing of submillimeter radiation guided by a dielectric sheet

Guided submillimeter radiation (=118.8 m) has been focussed by inserting a cylinder lens into the freely propagating beam in front of the incoupling prism. The beam profile at the focal spot has been determined experimentally, the results agree with theoretical predictions. The optical quality of the focus is good.     

A detailed rate equation model for the simulation of energy transfer in OH laser-induced fluorescence

A rate equation model (the LASKIN program packet) has been developed for the detailed computation of energy transfer in Laser-Induced Fluorescence (LIF). Calculations of this type are necessary for analysis of the influence of energy transfer processes [e.g., electronic quenching and Rotational Energy Transfer (RET)] on the fluorescence signal. The model has been utilized to examine linear LIF in the OHA ²⁺-X ² (0, 0) band. Available data on quenching, RET and spontaneous emission rates for the (A, v = 0) state have been reviewed, and models for the state-specific RET and quenching rates have been developed. The accuracy of the calculations has been confirmed by comparison with experimental data, and the LASKIN program has been applied to the analysis of potential error sources in the widely applied two-line LIF temperature-measurement technique. Extensions of the model to the examination of saturated LIF, OHA–X (1, 0) and (3, 0) excitation and LIF of other species (e.g., O₂ and NO) are discussed.     

The sign of the magnetic moment of191Pt(g.s.) determined by Mössbauer effect on oriented nuclei

Radioactive¹⁹¹Pt(3/2^–) alloyed to iron has been oriented at low temperature in a dilution refrigerator. The resonance absorption spectrum of the 82.4 keV transition of the polarized split source has been registered at high ( 1 K) and low ( 15 mK) temperatures. From the high temperature spectrum (E2/M1; 82.4) < 0 is established. From the positive-to-negative speed asymmetry of the low tempe rature spectrum we determined [191-Pt(g.s.)] > 0. This result is in agreement with deformed Hartree-Fock calculation predictions.     

A Low-Noise 230 GHz SIS Receiver for Radio Astronomy Employing Untuned Nb/AlOx/Nb Tunnel Junctions

A heterodyne receiver based on a 1/3 reduced height rectangular waveguide SIS mixer with two mechanical tuners has been built for astronomical observations of molecular transitions in the 230 GHz frequency band. The mixer used an untuned array (R_nC_j3, R_n70 ) of four Nb/AIOx/Nb tunnel junctions in series as a nonlinear mixing element. A reasonable balance between the input and output coupling efficiencies has been obtained by choosing the junction number N=4. The receiver exhibits DSB (Double Side Band) noise temperature around 50 K over a frequency range of more than 10 GHz centered at 230 GHz. The lowest system noise temperature of 38 K has been recorded at 232.5 GHz. Mainly by adjusting the subwaveguide backshort, the SSB (Single Side Band) operation with image rejection of 15 dB is obtained with the noise temperature as low as 50 K. In addition, the noise contribution from each receiver component has been studied further. The minimum SIS mixer noise temperature is estimated as 15 K, pretty close to the quantum limit v/k11 K at 230 GHz. It is believed that the receiver noise temperatures presented are the lowest yet reported for a 230 GHz receiver using untuned junctions.     

Modification of wetting properties of CR39 by plasma source ion implantation

Plasma source ion implantation (PSII), a hybrid implantation technique between ion beams and immersion plasmas has been used to modify CR39 surfaces for improved wettability providing both advancing (θ_a) and receding (θ_r) contact angles below 5°. The modifications brought to the polymer surface structure have been characterized by X-ray photoelectron spectroscopy (XPS) and its combination with chemical derivatization (CD-XPS). Oxygen desorption has been observed in spite of the very hydrophilic surfaces. C_1s XPS peak has been displaced toward greater energies, while the opposite has been found for O_1s, both involving new components and strong modifications after ion implantation treatment. Strong evidences about the formation of new chemical functions, like OOH, COOH and CC, have been found and have provided an explanation for the increased wettability.     

Gamma-radiation in the183Re decay

The gamma-ray intensities have been determined by means of Ge(Li) detectors. The previously proposed decay scheme has been tested using Ge(Li)- spectrometers. It has been found that the experimental data are not in disagreement with foregoing decay scheme. The comparison of the theoretical (if the Coriolis interaction is taken into account) and experimental gamma line intensity ratios is given.     

High-temperature UV absorption of methyl radicals behind shock waves

The absorption of ultraviolet narrow-line laser radiation by methyl radicals (CH₃) in the electronic system has been studied at high temperatures behind shock waves. Methyl radicals at high temperatures were generated by the shock heating of methyl precursors: azomethane, methyl iodide, and ethane. The spectral shape and intensity of the broadband absorption feature from 211.5 to 220 nm at high temperature (1565 K) has been measured. The absorption coefficient of CH₃ at 216.62 nm, the wavelength of peak absorption at high temperatures in the P+Q band, has been determined from 1200 to 2500 K. Additionally, the absorption coefficients of several interfering UV-absorbing combustion species (, and C₃H₆) have been determined at 216.62 nm.