A field-cycling NMR study of nematic 4-pentyl-4′-cyanobiphenyl confined in porous glasses

The proton spin-lattice relaxation time T₁, in the nematic liquid crystal 4-pentyl-4′-cyanobiphenyl confined in a glassy porous matrix has been measured in a wide Larmor frequency range of 1 · 10²?2 · 10⁷ Hz employing the fast field-cycling NMR technique. A strong influence of the restricted geometry on the character of the T₁ dispersion was found. Our investigation clearly demonstrates the importance of the translationally induced molecular reorientations in inhomogeneous director field for the relaxation in the samples with 200 and 80 nm mean pore size. The experimental results are in a good agreement with the theoretical predictions. In the sample with 7 nm pore size the main contribution to the relaxation is ascribed to the slowing down of the molecular motion in the near-surface layer. Zero-field 1H NMR spectra of a microconfined liquid crystal are reported for the first time.     

Resonance Scattering of GHz Plane Electromagnetic Waves from Ring Dielectric Linear Structures

Optics and Spectroscopy - Resonance backscattering at the fundamental magnetic mode and the wave properties of linear structures consisting of subwave dielectric elements in the form of planar thin...     

Temperature Non-Uniformity Along the Active Element of a He–Ne Laser

Russian Physics Journal - Temperature distribution along the discharge of a He–Ne laser is studied, its non-uniformity is detected, and possibility of its regulation is analyzed.     

A computational study of O-O bond formation catalyzed by mono- and bis-MnIV-corrole complexes

A detailed computational study of O-O bond formation, catalyzed by monomeric and dimeric Mn-corrole complexes, is reported. The model explicitly takes into account the solvent, with respect to the first and second coordination spheres, while the bulk solvent is described by the polarizable continuum model. Two reaction mechanisms are proposed and computationally characterized: the concerted and the two-step mechanisms. The concerted mechanism is based on a OH--MnIVO interaction via the outer-sphere pathway involving the bridging solvent molecules in the first coordinating sphere. The two-step mechanism is proposed to operate via the coordination of a hydroxide to the MnIV ion, forming a MnO(OH)--corrole complex with a strongly nonplanar corrole ligand. Comparison of the proposed mechanisms with available experimental data is performed.