Sapphire shaped crystals for waveguiding,sensing and exposure applications

Second half of the XX century was marked by a rapid development of sapphire shaped crystal growth technologies, driven by the demands for fast, low-cost, and technologically reliable methods of producing sapphire crystals of complex shape. Numerous techniques of shaped crystal growth from a melt have been proposed relying on the Stepanov concept of crystal shaping. In this review, we briefly describe the development of growth techniques, with a strong emphasize on those that yield sapphire crystals featuring high volumetric and surface quality. A favorable combination of physical properties of sapphire (superior hardness and tensile strength, impressive thermal conductivity and chemical inertness, high melting point and thermal shock resistance, transparency to electromagnetic waves in a wide spectral range) with advantages of shaped crystal growth techniques (primarily, an ability to produce sapphire crystals with a complex geometry of cross-section, along with high volumetric and surface quality) allows fabricating various instruments for waveguiding, sensing, and exposure technologies. We discuss recent developments of high-tech instruments, which are based on sapphire shaped crystals and vigorously employed in biomedical and material sciences, optics and photonics, nuclear physics and plasma sciences.     

Modeling of the Lipid Bilayer Mimicking the Inner Mitochondrial Membrane

Crystallography Reports - The model of the lipid bilayer mimicking the inner mitochondrial membrane was constructed. Each layer of the lipid bilayer model consists of 51 dilinoleoyl...     

Ab initio dipole moment and theoretical rovibrational intensities in the electronic ground state of PH3

We report a six-dimensional CCSD(T)/aug-cc-pVTZ dipole moment surface for the electronic ground state of PH₃ computed ab initio on a large grid of 10 080 molecular geometries. Parameterized, analytical functions are fitted through the ab initio data, and the resulting dipole moment functions are used, together with a potential energy function determined by refining an existing ab initio surface in fittings to experimental wavenumber data, for simulating absorption spectra of the first three polyads of PH₃, i.e., (ν₂, ν₄), (ν₁, ν₃, 2ν₂, 2ν₄, ν₂ + ν₄), and (ν₁ + ν₂, ν₃ + ν₂, ν₁ + ν₄, ν₃ + ν₄, 2ν₂ + ν₄, ν₂ + 2ν₄, 3ν₂, 3ν₄). The resulting theoretical transition moments show excellent agreement with experiment. A line-by-line comparison of the simulated intensities of the ν₂/ν₄ band system with 955 experimental intensity values reported by Brown et al. [L.R. Brown, R.L. Sams, I. Kleiner, C. Cottaz, L. Sagui, J. Mol. Spectrosc. 215 (2002) 178-203] gives an average absolute percentage deviation of 8.7% (and a root-mean-square deviation of 0.94 cm⁻¹ for the transition wavenumbers). This is very remarkable since the calculations rely entirely on ab initio dipole moment surfaces and do not involve any adjustment of these surfaces to reproduce the experimental intensities. Finally, we predict the line strengths for transitions between so-called cluster levels (near-degenerate levels formed at high rotational excitation) for J up to 60.     

Preparation and photophysical studies of a fluorous phase-soluble fullerene derivative

We report the first synthesis of a well-characterized "Teflon ponytail" fullerene adduct (3) via the Hirsch-Bingel reaction with a malonate bearing two perfluorinated alkyl chains. This C3 tris-adduct shows excellent solubility in perfluorinated solvents, such as FC-72 and FC-75. Compound 3 was found to be an efficient sensitizer for singlet oxygen formation in fluorous media, which has potential in biphasic systems and in photobiology.     

Mechanisms of C—H Activation in Alkanes by Chromium-Oxo Reagents

The mechanisms of activation of a C—H bond by chromium-oxo reagents in the reactions of methane, isobutane, adamantane, and protoadamantane with CrO₂(OH)₂ were investigated by the BH&HLYP quantum-chemical method in the 6-31G^* and 6-311G^** (for Cr) basis sets. It was shown that the transition states have clearly defined biradical character and significant transfer of charge from the hydrocarbon to the electrophile.