The origin of localized vibrations in KI: Cl and KI: H crystals

The resonant, gap, and local vibrational modes of Cl and H impurities in KI crystals are calculated recursively using the shell model. The contributions from ions located in various coordination shells around the impurity to the formation of localized vibrations are studied. The results of the calculations are in satisfactory agreement with the experimental data.     

Analysis of the form of ultrashort pulses by spectral nonlinear interferometry

A new method for recording the phase structure of ultrashort optical pulses is proposed that makes no use of a reference pulse. Using three-wave interactions in a nonlinear optical medium, a wave of spectral decomposition of an ultrashort pulse is transformed into a monochromatic wave. The spatial phase structure of this wave contains information on the phase structure of the pulse spectrum and on the pulse form. This structure is analyzed by shearing interferometry.

     

Formyl MIDA Boronate: C1 Building Block Enables Straightforward Access to α‐Functionalized Organoboron Derivatives

Formyl MIDA boronate has been known to be an elusive type of acylboronate that has not been obtained to date. In this work, an approach to the one‐pot preparation and chemical transformations of formyl MIDA boronate were developed to provide new types of α‐functionalized organoboron compounds. Among them are acylboronate reagents which present boron‐substituted analogues of ynones and β‐dicarbonyl compounds. The developed synthetic procedures, utilizing formyl MIDA boronate, are tolerant to diverse functional groups, making this reagent an advantageous C₁ building block for extending the scope of organoboron chemistry.     

Interaction of nickel donor and acceptor excitons with defect vibrations in ZnSe:Ni crystals

Defect vibrations in ZnSe:Ni crystals induced by the Ni impurity with charge of ±1 relative to the neutral state are calculated by a recursive method in the shell model. This leads to an interpretation of vibronic structures in electroabsorption spectra for donor and acceptor Ni excitons in ZnSe:Ni crystals. Fiz. Tverd. Tela (St. Petersburg) 39, 2147–2151 (December 1997)     

Anomalous influence of magnetic field on the indirect exciton in GaAs/AlGaAs double quantum wells

A study is reported of exciton luminescence in GaAs double quantum wells produced in electric and magnetic fields. It has been found that the indirect-exciton line (IX) behaves anomalously, namely, one observes a magnetic-field-induced low-energy shift of the IX line, and the onset of periodic (≈5 s) fluctuations in the IX-line intensity. Fiz. Tverd. Tela (St. Petersburg) 40, 803–805 (May 1998)     

Model of the lattice dynamics and study of the vibronic structure of intracenter transitions in ZnO:Ni+2 crystals

This paper presents a calculation of the defect vibrations induced in a ZnO:Ni crystal by the Ni⁺² impurity. The computations are done by a recursive method in the shell model. Based on the model calculations, the vibronic structure in the absorption spectra of the intracenter d-d transitions in the ZnO:Ni crystal is interpreted. Fiz. Tverd. Tela (St. Petersburg) 40, 2213–2216 (December 1998)     

Simulation of the electronic structure of simple oxides BeO and SiO2 and complex oxides Be2SiO4 and Be2SixGe1 ? xO4 with the phenacite structure

The ab initio numerical calculations of the electronic structure of simple oxides BeO and SiO₂ and complex oxides Be₂SiO₄ and Be₂Si _x Ge_{1 − x} O₄ with the phenacite structure have been performed using the electron density functional theory. The calculations indicate that the main feature of the systems under investigation is the presence of oxygen states in both the valence and conduction bands. The splitting of the bottom of the conduction band has been revealed in the electronic structure of the Be₂Si _x Ge_{1 − x} O₄ system. The splitting width is about 1.5 eV. The main contribution to the formation of a narrow subband of the conduction band comes from the 2s and 2p states of oxygen and the 4d state of germanium. Microscopic models of the spatial localization of the electron density on lower energy states of the conduction band of oxide crystals have been developed using the Wannier function technique. The reflection spectra of BeO, SiO₂, and Be₂SiO₄ have been analyzed. The reported calculations of the electronic structure imply the exciton nature of the 9.7-eV reflection peak in the Be₂SiO₄ crystal.