Lattice modes of the chirally pure and racemic phases of tyrosine crystals

High-Q librational modes have been found to be present in the infrared absorption and Raman spectra of chirally pure L-tyrosine. Such modes can serve as terahertz radiation detectors and generators in chirally pure biostructures.     

Accurate Crystal Structure Refinement of Natrolite and Localization of Free Water

Crystallography Reports - Crystals that contain water molecules spaced by distances excluding their chemical interaction are model systems for studying the so-called “water...     

Boron 10B—11B Isotope Substitution as a Probe of the Mechanism Responsible for the Record Thermionic Emission in LaB6 with the Jahn—Teller Instability1

We have tested the conduction band electrons of lanthanum hexaboride that is among the most effective electron-beam sources with one of the highest brightness of thermionic emission. We performed infrared spectroscopic, DC (direct current) resistivity and Hall-effect studies of LaB₆ single crystals with various ¹⁰B and ¹¹B isotope contents. We find that only a small amount of conduction electrons behave as Drude-type charge carriers while about 70% of the electrons are involved in collective oscillations of electron density coupled to vibrations of both the Jahn-Teller unstable rigid boron cage and rattling modes of La-ions loosely bound to the lattice. We suggest that exactly these non-equilibrium conduction electrons determine the extraordinary low work function of thermoemission in LaB₆.

     

Dispersion relations of hybrid waves in dielectric media

The dispersion relations of hybrid waves—polaritons, scalar bosons (hiddennons) and pseudoscalar bosons (axinons)—in one-dimensional dielectric media are derived with allowance for the resonant interaction between mechanical excitations of crystal lattices and elementary excitations of vacuum. It is shown that in the range of small wave vectors hybrid quasi-particles are formed in dielectric media: polaritons, hiddennons and axinons. For sodium nitrite crystal, dispersion relations of such hybrid quasiparticles are calculated near the center of the Brillouin zone. The resulting dispersion relations of hybrid quasi-particles provide conditions that allow observation of conversion of vacuum photon-like particles into hybrid quasi-particles in dielectrics, and also of parametric light scattering accompanied by the generation of hybrid quasi-particles.     

Laser spectroscopy and dynamics of crystal lattices of chirally pure and racemic phases of amino acids

Strong sharp lines due to the librational modes characterized by a pseudoscalar symmetry type have been found in the low-frequency Raman spectra of the lattices of glycine and tyrosine amino acids. The intensities of these lines exceed those for Raman scattering in the region of intramolecular vibrations. The spectra of chirally pure and racemic phases of amino acids differ significantly. The results obtained can be used to observe stimulated Raman scattering from the librational modes of crystalline amino acids and monitor the chiral purity of bioactive preparations containing amino acids.