Experimental and theoretical study of reaction of OH with 1,3-butadiene

The kinetics of the reaction of hydroxyl radical with 1,3-butadiene at 240-340 K and a total pressure of approximately 1 Torr has been studied using relative rate combined with the discharge flow and mass spectrometer technique. The reaction dynamics of the same reaction has also been investigated using ab initio molecular orbital theory. The rate constant for this reaction was found to be negatively dependent on temperature, with an Arrhenius expression of k1 = (1.58 +/- 0.07) x 10(-11) exp[(436 +/- 13)/T] cm3 molecule(-1) s(-1) (uncertainties taken as 2sigma), which was in good agreement with that reported by Atkinson et al. and Liu et al. at 299-424 K. Mass spectral evidences were found for the addition of OH to both the terminal and the internal carbons of 1,3-butadiene. Our computational results suggest that both addition of OH to 1,3-butadiene and the abstraction of hydrogen atom from 1,3-butadiene by the OH radical are exothermic processes and that the addition of OH to the terminal carbon of the 1,3-butadiene is predicted to have an activation energy of 0.7 kcal mol(-1), being the most energetically favored reaction pathway.     

Critical behavior of magnetic thin films

We study the critical behavior of magnetic thin films as a function of the film thickness. We use the ferromagnetic Ising model with the high-resolution multiple histogram Monte Carlo (MC) simulation. We show that though the 2D behavior remains dominant at small thicknesses, there is a systematic continuous deviation of the critical exponents from their 2D values. We explain these deviations using the concept of “effective” exponents suggested by Capehart and Fisher in a finite size analysis. The shift of the critical temperature with the film thickness obtained here by MC simulation is in an excellent agreement with their prediction.     

Picosecond measurements of the third order susceptibility tensor in liquids

Single frequency Jamin interferometry is used for observation of non-linear susceptibility tensor measurements in the picosecond range (25 ps). At low density, when avoiding the polarization state instabilities, the displacement of the fringes leads to the measurement of two components of the nonlinear susceptibility tensor. It is shown that X_xyyx (ω = ω + ω - ω) decreases when the pulse duration is reduced, whereas X_{xxxx (ω = ω + ω - ω)} remains constant. This is interpreted by the difference between the orientational and vibrational molecular contributions.     

Polar Kerr rotation spectra in yttrium iron garnet and lithium ferrite: A comparative study

Polar Kerr rotation (PKR) spectra in the range 2.0–5.7 eV at 295 K of lithium ferrite and yttrium iron garnet (YIG) single crystals are reported. The spectra show more details and cover a more extended energy region than those published so far. The interpretation of the spectra is based on the assumptions that 1) PKR is an odd function of the sublattice magnetic moments 2) the origin of PKR in both compounds is of similar nature, the differences due to the different crystal structures (garnet and spinel) being less important. The calculated PKR sublattice components show some similarities in their energy dependences, the magnitude of the tetrahedral sublattice component being higher than that of the octahedral one. The components were used in the calculation of the PKR spectra in diamagnetically substituted yttrium iron garnet (J. Appl. Phys.49, 2212, 1978). The results correctly predict the trends observed experimentally.     

Magnetic anisotropy of the Y(Co1-xFex)3 pseudobinary compounds

The anisotropy energy of the Y(Co_{1 - x}Fe_x)₃ compounds has been determined between 4.2 and 250 K. The concentration dependence of the anisotropy energy behaves anomalously in this pseudo-binary series. Upon increasing the iron content, the anisotropy energy increases up to x = 0.25, then decreases, changes sign around x = 0.45 and reaches a flat minimum at the iron-rich side. This anomaly can satisfactorily be explained in terms of the individual site anisotropy model by considering the different occupancy factors of iron and cobalt for the 3d sites.     

Propagation in media with Raman-type nonlinearity: polarization states of the waves and gains

The simultaneous propagation of laser and Raman waves through nonlinear media is theoretically studied using the nonlinear third-order susceptibility tensor formalism. Polarization states and gains with linearly, circularly and elliptically exciting polarizations are calculated. The theoretical expressions are compared with experimental results in the absence of self focusing. The perturbations due to self focusing near the stimulated Raman scattering thresholds are studied and conclusions concerning the anisotropy of the Kerr constant are obtained.     

Radiative electronic transitions in ZnTe∶Al,Ga, in crystals

We report the results of studies on the concentration dependence of the cathodoluminescence of ZnTe:Al, Ga, In crystals in the temperature range 4.2–300 K. A band with maximum at 2.2 eV and half-width of the order of 70 MeV and a band with maximum at 2.36 eV and half-width 1 MeV appear in ZnTe:Al crystals at 4.2 K. In the temperature range 40–70 K we detected the structure of the first band such that the separation of the maxima of the resolved bands corresponded to the energy of an LO phonon. A band with maximum at 1.8 eV was found to appear in ZnTe:Ga crystals at 4.2 K and a band with maximum at 1.9 eV appeared in ZnTe:In crystals at that temperature. The donor activation energies were determined to be 0.11, 0.30, and 0.25 eV, respectively, for aluminum, gallium, and indium.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 82–86, October, 1987.     

Analytical predictions of exergoeconomic performance of a solar air heater with surface roughness of metal waste

Journal of Thermal Analysis and Calorimetry - The current study is the authors’ next work from the perspectives of the second law and economics of an air collector having artificial roughness...     

Application of Quantum Gauss-Jordan Elimination Code to Quantum Secret Sharing Code

International Journal of Theoretical Physics - The QSS codes associated with a MSP code are based on finding an invertible matrix V, solving the system $\mathbf {v}_{A}^{T}M_{B} \left (\begin...     

Synthesis of alginate stabilized gold nanoparticles by γ-irradiation with controllable size using different Au3+ concentration and seed particles enlargement

Gold nanoparticles with pre-selected size in the range 5–40 nm were synthesized by γ-irradiation of Au³⁺ solution containing natural polysaccharide alginate as a stabilizer. The gold nanoparticles with controllable size were prepared by two approaches: (i) varying the concentration of Au³⁺ from 0.25 to 1 mM and alginate from 0.25% to 1% (w/v) and (ii) enlargement of seed particles with double size from 20 to 40 nm at [Au³⁺]/[Au⁰]=6. The obtained gold nanoparticles were characterized by UV–vis spectroscopy and transmission electron microscopy. The results indicated that γ-irradiation method is suitable for production of gold nanoparticles with controllable size and high purity.