X-ray diffraction analysis of double-layer systems irradiated by a high-power ion beam

Systems of thin Ni films on a copper substrate, thin Ni films on an aluminum substrate, and St20 steel covered with graphite irradiated by a high-power ion beam of nanosecond duration have been investigated by x-ray diffractometry. The mixing of nickel with aluminum and St20 steel with graphite is revealed. It is shown that the mixing predominantly occurs in the liquid phase and depends on the thermal properties of a film and substrate.     

Flexo-electric polarization and anchoring energy for a nematic liquid crystal in a hybrid cell

Summary The flexo-electric polarization of hybrid nematic cells filled with 5 CB was measured as a function of cell thickness. To this aim the pyroelectric response of a nematic layer with small amount of light absorbing dye dissolved was detected in a nematic temperature range. From the experimental data the angle of the director deviation at the homeotropic boundary was calculated as a function of cell thickness. This dependence allows the qualitative determination of the shape of the potential well for the director deviation which is inconsistent with Rapini’s sinesquared form. The ?apparent? Rapini’s anchoring energy varies with a surface director angle (at the homeotropic boundary) from 5·10⁻³ to 3.5·10⁻² erg·cm⁻². Work presented at the second USSR-Italy Bilateral Meeting on Liquid Crystals held in Moscow, September 15–21, 1988.     

Spectral characteristics and molecular polarizabilities of ground and excited electronic states of thin tetraphenylporphyrin films

We present the results of spectral investigations of optical and dielectric characteristics of solid Langmuir films of meso-substituted palladium tetraphenylporphyrin. Based on these characteristics, the spectrum of the polarizability α _g of the ground state of the molecule has been obtained. Necessary Lorentz corrections that take into account the local field of the electromagnetic wave acting on the molecule have been introduced into the spectra of the absorption coefficient. Using the spectral method of electroabsorption, the differences of the polarizabilities Δα _i = α _ei ? α _g (i = 1, 2, 3) for the three excited states of the molecule α _ei have been found, and their frequency spectra in narrow ranges near resonances have been shown.     

HMBC‐1,n‐ADEQUATE spectra calculated from HMBC and 1,n‐ADEQUATE spectra

Unsymmetrical and generalized indirect covariance processing methods provide a means of mathematically combining pairs of 2D NMR spectra that share a common frequency domain to facilitate the extraction of correlation information. Previous reports have focused on the combination of HSQC spectra with 1,1‐, 1,n‐, and inverted ¹J_CC 1,n‐ADEQUATE spectra to afford carbon–carbon correlation spectra that allow the extraction of direct (¹J_CC), long‐range (ⁿJ_CC, where n ≥ 2), and ¹J_CC‐edited long‐range correlation data, respectively. Covariance processing of HMBC and 1,1‐ADEQUATE spectra has also recently been reported, allowing convenient, high‐sensitivity access to ⁿJ_CC correlation data equivalent to the much lower sensitivity n,1‐ADEQUATE experiment. Furthermore, HMBC‐1,1‐ADEQUATE correlations are observed in the F₁ frequency domain at the intrinsic chemical shift of the ¹³C resonance in question rather than at the double‐quantum frequency of the pair of correlated carbons, as visualized by the n,1, and m,n‐ADEQUATE experiments, greatly simplifying data interpretation. In an extension of previous work, the covariance processing of HMBC and 1,n‐ADEQUATE spectra is now reported. The resulting HMBC‐1,n‐ADEQUATE spectrum affords long‐range carbon–carbon correlation data equivalent to the very low sensitivity m,n‐ADEQUATE experiment. In addition to the significantly higher sensitivity of the covariance calculated spectrum, correlations in the HMBC‐1,n‐ADEQUATE spectrum are again detected at the intrinsic ¹³C chemical shifts of the correlated carbons rather than at the double‐quantum frequency of the pair of correlated carbons. HMBC‐1,n‐ADEQUATE spectra can provide correlations ranging from diagonal (⁰J_CC or diagonal correlations) to ⁴J_CC under normal circumstances to as much as ⁶J_CC in rare instances. The experiment affords the potential means of establishing the structures of severely proton‐deficient molecules. Copyright © 2013 John Wiley & Sons, Ltd.     

Scattering and amplification of light in a layer of a nematic liquid crystal

The role of light scattering in liquid crystal lasers can be of two kinds. It can induce undesirable losses increasing the lasing threshold or it can promote the appearance of feedback necessary for lasing. The light amplification spectra of the liquid crystal in the isotropic and light-scattering nematic phases have been measured. For comparison, at a close pump power, the amplification spectra have been measured on a TiO₂ nanoparticle suspension in an isotropic solvent, where the mean free path of photons is the same as that in the liquid crystal. The amplifications in two systems are significantly different, because the shapes of their scattering patterns are strongly different.     

Search for lepton flavor violating decays tau+/--->l+/-omega

A search for lepton flavor violating decays of a tau to a lighter-mass charged lepton and an omega vector meson is performed using 384.1 fb(-1) of e(+)e(-) annihilation data collected with the BABAR detector at the Stanford Linear Accelerator Center PEP-II storage ring. No signal is found, and the upper limits on the branching ratios are determined to be B(tau(+/-)-->e;{+/-}omega)<1.1 x10 (-7) and B(tau(+/-)-->micro(+/-)omega)<1.0 x 10(-7) at 90% confidence level.