High-resolution vibrational spectroscopy of the OH− ion in an Mg-related defect in LiF and NaF

Summary High-resolution (0.05 cm⁻¹) FTIR spectroscopy in the range (9÷300) K is applied to study the vibrational (stretching, bending and combination) modes of OH⁻ (and its isotopic substitution with OD⁻) perturbed by a neighbouring defect induced by Mg²⁺ in LiF and NaF. The stretching-mode spectra are analysed in the framework of the anharmonic-oscillator model: the related Morse parameters have been determined. A model is proposed for the defect, responsible for the stretching line and two bending lines, which are accounted for by an inversion doubling. In honour of Prof. Fausto Fumi on the occasion of his retirement from teaching.     

A power-law model of the pseudopotential

A new simple power-law model of the pseudopotential is suggested. The parameters of the pseudopotential are determined for ions of the second period of the periodic system. Excited energy levels calculated for these ions using this model demonstrate its convergence. The accuracy of the energy levels calculated for the excited states is <10⁻³ a.u.     

Relaxation of electronically excited products of solid-state reactions in the crystal lattice

The mechanisms of deactivation of electronically excited products of decomposition of silver azide (nitrogen molecules) are examined. A model of dipole interaction with the electron subsystem of the crystal is used to estimate the rate constants of deactivation with formation of electron-hole pairs (∼10⁹ s⁻¹) and energy transfer to a band hole (∼10⁻¹² cm³ s⁻¹). The values obtained confirm the basic postulate underlying the models of solid-phase chain reactions: the preferential formation of electronic excitations of the crystal lattice during the deactivation of excited decomposition products.     

Characteristics of the AT-303 hypersonic wind tunnel. Part 2. Aerodynamics of the HB-2 reference model

Aerodynamic coefficients of the HB-2 AGARD reference model measured in a new AT-303 hypersonic wind tunnel with adiabatic compression are presented. The experiments are performed in the ranges of Mach numbers M = 9.7 − 15.6 (Re_d = 0.14·10⁶ − 1.32·10⁶) and angles of attack α = −4°−12° with the use of an internal six-component strain-gauge balance. The technique used for processing and correcting measured results, which takes into account the dynamic properties of the model and the specific features of the nozzle structure, is described in detail. The aerodynamic coefficients obtained for this model are compared with similar data obtained in wind tunnels of Germany, France, and the USA.     

Recoil distance half-life measurements of the excited states in 145Sm

A recoil distance method was used to measure half-lives of the excited states of ₁₄₅Sm. The reaction used was ₁₃₉La(₁₀B, 4n)₁₄₅Sm. A plunger system was used. Half-lives were determined for two excited states for the first time. The yrast 27/2₊ state was found to have a half-life of 1.1 ± 0.2 ns corresponding to the retardation of 3.1 × 10₋₄ comparing with the single particle estimate of M1. The excitation energy of this state was well reproduced by the shell model calculation having a mixed configuration of [π{h^11/2(g^7/2)₋₂ (d^5/2)₋₁}¹⁰⁻, νf^7/2] + [π{h^11/2(g^7/2)₋₁}⁹⁻,νh^9/2]. Another retarded E1 transition was also found in a decay of a 21/2₊ state. Its retardation was 1.6 × 10₋₄ comparing with the single particle value. Received: 9 September 1997 / Revised version: 12 June 1998     

Model of metal surface erosion under irradiation by high-power pulsed ion beams

The mechanisms of erosion of metal surfaces under the action of submicrosecond (10⁻⁹−10⁻⁶ s) ion beams in the power density range of P = 10⁶−10⁹ W/cm² with a particle energy of 1–2000 keV are considered. It is shown that the collective processes associated with the radiation heating of the surface are of great importance. A model for the erosion is proposed. In accordance with this model, the flow of atoms of the target leaving the surface being irradiated consists of two independent components caused by collisional sputtering and evaporation, respectively. The influence of the irradiation parameters on the erosion coefficient and the ratio between the sputtering and evaporation factors is analyzed.     

Spectrofluorimetric Assessment of Doxycycline Hydrochloride in Pharmaceutical Tablets and Serum Sample Based on the Enhancement of the Luminescence Intensity of the Optical Sensor Sm<Superscript>3+</Superscript> Ion

A simple and sensitive spectrofluorimetric method for determination of trace amount of doxycycline hydrochloride (DC) in pharmaceutical tablets and serum samples was developed. In ammonia buffer solution of pH 8.9 the doxycycline hydrochloride can remarkably enhance the luminescence intensity of the Sm³⁺ ion in Sm³⁺- DC complex at λ_ex = 400 nm. The produced luminescence intensity of Sm³⁺- DC complex in DMSO is in proportion to the concentration of DC and used as optical sensor for its determination. The dynamic range for the determination of DC is 1 × 10⁻⁸ – 5 × 10⁻⁶ mol L⁻¹ and in case of quantum yield calculations is 7 × 10⁻⁹ – 5 × 10⁻⁶ mol L⁻¹ with detection limit of 6.5 × 10⁻¹⁰ mol L⁻¹. The enhancement mechanism of the luminescence intensity in the Sm³⁺- DC system has been also discussed. A comparison with other spectrofluorimetric methods for tetracycline derivatives in which Eu³⁺ ion is used instead of Sm³⁺ ion is also studied.     

Synthetic spectrum of the stratosphere in the submillimeter region

A line-by-line and layer-by-layer optimized method is used for the fast computation of new high resolution spectra in the submillimeter region for the stratospheric medium. The results are shown as synthetic spectra between 10 and 40 cm⁻¹ and the presence of lines of minor gaseous constituents in the stratospheric medium is indexed. The purpose of the calculations is to determine better the spectral emission (better than 1 %) with a minimum computation time (less than 1’/cm⁻¹). The high resolution spectra (5.10⁻⁴ cm⁻¹) show excellent submillimeter emission lines; this opens a wide field of investigation for stratospherical studies.     

Model and simulation method for the nonlinear radiation response of a metal-oxide-semiconductor transistor structure

A simplified physical model is proposed, together with a method of nonlinear simulation for the shift in the threshold voltage of a transistor MOS structure under time-varying irradiation and with varying parameters for the external conditions. Simple calculations from the model are compared with experimental data for transistors made to be radiation-stable at dose rates of 2·10⁹-0.012 rad/sec for times of 10⁻⁶–10⁻⁷ sec. Flaw Detection Research Institute, Tomsk Polytechnical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 52–58, July, 1996.     

Electrochemical properties of a proton conducting polymer

Electrochemical, optical and thermal characterisation of a proton conducting polymer system based on poly(2-acrylamido-2 methyl-propane-sulfonic acid) (Poly-AMPS) for use in electrochromic windows is reported. The polymer electrolyte has been obtained by cross-linking branched poly(ethylene imine) with the 2-acrylamido-2 methyl-propane-sulfonic acid. The conductivity of the poly-AMPS films is influenced by the water content in the membrane and can vary between 10⁻⁴ and 10⁻⁷ Ω⁻¹ cm⁻¹. A minimum activation energy of 17±3 kJ/mol is estimated by a simple Arrhenius model. Poly-AMPS is very sensitive to the humidity in the surroundings and electrochromic windows should be sealed if poly-AMPS is used. Temperatures above 45–50 °C give increasing cracks in the polymer and loss of adhesion to the electrode surface. Paper presented at the 4th Euroconference on Solid State Ionics, Renvyle, Galway, Ireland, Sept. 13–19, 1997     

A Model of spin catalysis in bacterial photosynthetic reaction centres

A model of influence of non-heme Fe²⁺ ion on kinetics of electron transfer between quinone anion-radicals Q_A⁻ and Q_B⁻ in bacterial reaction centres is proposed and investigated. Physical mechanism of the influence is associated with singlet-triplet transitions in Q_A⁻Q_B⁻ Pair caused by interactions with paramagnetic Fe²⁺. The model incorporates exchange couplings between the particles and zero-field splittings in high-spin Fe²⁺. These interactions are shown to catalyze electron transfer in triplet pairs and alter the reaction yield significantly.     

Antikaon angular distributions in the reaction γd → K −Θ+ p → K − K + np near the threshold and the parity of the Θ+ Pentaquark

Within the spectator model, we study the reaction γd → K ⁻Θ⁺ p → K ⁻ K ⁺ np in the threshold energy region. We present the predictions for the exclusive and inclusive K ⁻-meson angular distributions in the laboratory system for this reaction calculated for two possible parity states of the Θ⁺ resonance at 1.5-and 1.75-GeV beam energies with and without imposing the relevant kinematical cuts on those parts of the sampled phase space where the contribution from the main background sources, associated with the ϕ(1020), Λ(1520) production as well as with the K ⁻ p rescattering in the final state, is expected to be dominant. We show that, under the chosen kinematics, these distributions are sensitive to the Θ⁺ parity and, therefore, can be used as a filter for the determination of its parity. The text was submitted by the author in English.     

On the polarization measurements of the Mössbauer gamma-rays

Summary A theoretical analysis of polarization of the M?ssbauer radiation has been attempted by using the Stokes parametrization technique. Explicit results for theM1 (3/2⁻→1/2⁻) andE2 (2⁺→0⁺) radiations in relation to polarization and hyperfine-field parameters in the crystal fixed-axis system are discussed. To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.     

Production of transuranium elements in a binary model under conditions of pulse nucleosynthesis

A model for the production of transuranium isotopes under the conditions of pulse nucleosynthesis in a powerful neutron flux (∼10²⁴−10²⁵ neutron cm⁻²) is considered. The explosive nature of the process allows us to separate it into two parts: the process of multiple neutron captures (t < 10⁻⁶ s) and the process of the subsequent β-decays for neutron-rich nuclei. The model of multiple captures neutron includes a variation of the cross section of the (n, γ) reaction as a result of the adiabatic expansion of the explosive nucleosynthesis area. A binary mixture of ²³⁸U and ²³⁹Pu is used as the initial isotope composition.     

Thermal conductivity of the diamond-paraffin wax composite

The thermal conductivity of diamond-paraffin wax composites prepared by infiltration of a hydrocarbon binder with the thermal conductivity λ _m = 0.2 W m⁻¹ K⁻¹ into a dense bed of diamond particles (λ _f ∼ 1500 W m⁻¹ K⁻¹) with sizes of 400 and 180 μm has been investigated. The calculations using universally accepted models considering isolated inclusions in a matrix have demonstrated that the best agreement with the measured values of the thermal conductivity of the composite λ = 10–12 W m⁻¹ K⁻¹ is achieved with the use of the differential effective medium model, the Maxwell mean field scheme gives a very underestimated calculated value of λ, and the effective medium theory leads to a very overestimated value. An agreement between the calculation and the experiment can be provided by constructing thermal conductivity functions. The calculation of the thermal conductivity at the percolation threshold has shown that the experimental thermal conductivity of the composites is higher than this critical value. It has been established that, for the composites with closely packed diamond particles (the volume fraction is ∼0.63 for a monodisperse binder), the use of the isolated particle model (Hasselman-Johnson and differential effective medium models) for calculating the thermal conductivity is not quite correct, because the model does not take into account the percolation component of the thermal conductivity. In particular, this holds true for the calculation of the heat conductance of diamond-matrix interfaces in diamond-metal composites with a high thermal conductivity.     

The effect of the scale factor on the focusing properties of a vortex gas flow

An experimental study is carried out to investigate a bilateral direct-flow vortex tube of small (0.3–3.0)·10⁻² m) size and to compare its optical properties with those characteristics of vortex tubes of a larger ((3–16)\10⁻² m) scale. A model is suggested for forming transverse profiles of the intensity of laser beams with an intensity hole in the center and of annular beams. Translated from Zhural Prikladnoi Spektroskopii, Vol. 64, No. 3, pp. 386–389, May–June, 1997     

Field dispersion in parametrically excited oscillator upon relaxation

A complete system of solutions of the equation describing the parametric excitation of an oscillator is presented. This system makes it possible to take into account losses in a parametrically excited oscillator in terms of the perturbation theory. It is shown that, although the oscillator losses are small (the relative spectral width of a typical laser cavity is 10⁻⁸), they limit the achievable squeezing coefficients by values on the order of ten. At present, the progress in resonator technique allows one to achieve relative spectral widths on the order of 10⁻¹¹–10⁻¹². Therefore, it can be expected to achieve squeezing coefficients on the order of 10³.     

Fluorescence Enhancement Effect for the Determination of Polychlorinated Biphenyls with Bovine Serum Albumin

A sensitive and selective method for the trace determination of 3, 3’, 4, 4’-tetrachlorobiphenyl (PCB77) by using bovine serum albumin (BSA) as a fluorescence probe was introduced. Under optimum conditions, the enhanced fluorescence intensity was proportional to the concentration of polychlorinated biphenyls in the range of 8.9 × 10⁻⁸–5.0 × 10⁻⁶ mol L⁻¹ for PCB77, and 5.0 × 10⁻⁷–5.0 × 10⁻⁶ mol L⁻¹ for 2, 2’, 5, 5’-tetrachlorbiphenyl (PCB52). The detection limits (S/N = 3) of PCB77 and PCB52 were 2.6 × 10⁻⁸ mol L⁻¹ and 2.9 × 10⁻⁷ mol L⁻¹, respectively. Furthermore, the fluorescence enhancement mechanism was discussed in detail. Results indicated that fluorescence enhancement of the system originated from the formation of BSA-PCBs complexes. In addition, PCBs were mainly bound to the tyrosine residues in BSA molecules.     

Velocity-dependent inertial induction and secular retardation of the earth’s rotation

According to the model of inertial induction proposed earlier, the inertia force consists of an acceleration-dependent term which comes out as identically equal to -ma. Besides, there is a velocity-dependent term which is exceedingly small to be easily detected. However, it has been shown that this results in a cosmological red shift of light coming from distant stars and galaxies; the magnitude of the red shift agrees very well with the observed values. Though this model yields correct results when applied to photons it needs modification before applying to other bodies. A modified form of the inertial induction model is now proposed where the proposed velocity-dependent inertia forces, when applied to the solar system, yields correct order of magnitude for the secular retardation of the earth’s rotation. Moreover, a combined model using the velocity term and the tidal friction also does not suggest any close proximity of the moon to the earth in the past. When the model is applied to the case of Phobos, a secular acceleration of the order of magnitude of 10⁻³ deg yr⁻² is obtained.