The nature of activation centers in Y2SiO5:Pr3+, Gd2SiO5:Pr3+, and Lu2SiO5:Pr3+ crystals

A complex study of the energy spectra and relaxation channels for the excitation energy of activation centers in Y₂SiO₅:Pr³⁺, Lu₂SiO₅:Pr³⁺, and Gd₂SiO₅:Pr³⁺ was performed. An analysis of the low-temperature optical spectra showed that the energy parameters and the character of field splitting of the ¹ D ₂ and ³ H ₄ activator ion terms were substantially different in crystals of different crystallographic types. The pseudosymmetry effect was observed in splitting of the ¹ D ₂ and ³ H ₄ terms of Pr³⁺ ions situated in nonequivalent crystal lattice cation sites of Y₂SiO₅ and Lu₂SiO₅. Activator ions nonuniformly populated nonequivalent cation sites of the Y₂SiO₅ crystal lattice. At high activator ion concentrations (>1 at %), luminescence decay in Y₂SiO₅ could not be described by a simple exponential time dependence. The complex luminescence decay law was caused by activator ion excitation energy migration and capture by acceptors. The role of energy acceptors was played by activator ion dimers.     

Reaction of l-aryl-δ2-pyrazoline salts with lithium aluminum hydride

The corresponding pyrazolidines were obtained by reduction of 1-aryl(1-hetaryl)pyrazoline salts. The structure of the products and the reaction mechanism are discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 547–550, April, 1973.     

Low-frequency vibrational motions in proteins: Physical mechanisms and effect on functioning

A possibility for the low-frequency (terahertz) vibrational motions of large parts of protein molecules is considered and the characteristic frequencies are estimated. The problem of damping of these motions is discussed and the effect of solvent molecules on the model low-frequency molecular oscillators is experimentally studied using Raman spectroscopy. The data obtained show that the effect of solvent is not reduced to a decrease in the Q factor and causes variations in frequencies and relative amplitudes of the low-frequency oscillations.