Interaction of excitons in indirect solid solutions of In1−xGaxP at high levels of excitation

The cathode luminescence spectra of GaP and solid solutions of In_1–xGa_xP (with an indirect energy band structure) obtained by liquid-phase epitaxy are investigated at T=77 and 9°K. It is established that the recombination of excitons on neutral donors and the pure exciton recombination with the participation of TA (=13±1 meV), LA (=31±1 meV), and TO (=43±2 meV) phonons. dominate in the low-temperature luminescence spectra of GaP and In_1–xGa_xP with a small concentration of photon impurities. The complex luminescence band that arises for sufficiently high levels of excitation and at T = 9°K is attributed to the luminescence of an electron-hole drop (EHD). The transformation of spectral form of the EHD band with the transition from GaP to In_1–xGa_xP is attributed to a simultaneous reduction in the contribution of the TA and TO replicas and to the appearance of a phononless component in the luminescence of the EHD.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 37–40, September, 1985.     

The absolute value of the rate constant of the liquid-phase reaction SO 5 −. + Fe(II)

An analytical method for monitoring the Fe²⁺ concentration during liquid-phase sulfite oxidation catalyzed by iron ions is described. The concentration conditions under which the Fe(III)/Fe(II) ratio is uniquely related to the rate constant of the reaction SO ₅ ^?. + Fe²⁺ are found by computer analysis. The experimental and calculated Fe(III)/Fe(II) ratio data are in agreement at $k_{(SO_5^{ - \cdot } + Fe^{2 + } )} = 3.2 \times 10^6 1mol^{ - 1} s^{ - 1} $ . This is one of the three rate constant values known from the literature, which differ by a factor greater than 70.     

N‐Methyl‐trimethylacetamide in Thin Films Displays Infrared Spectra of π‐Helices,with Visible Static and Dynamic Growth Phases,and then a β‐Sheet

The simplest (minimal) peptide model is HCONHCH₃. An increase in the π‐helix content with increased substitution in the acyl portion suggested the examination of N‐methyl‐trimethylacetamide) (NMT). NMT displays spectra, in which there is evolution of a set of helices defined by their amide I maxima near 1686 (3₁₀), 1655 (first π), and, most importantly, at 1637 cm^?1 (π). Expanded thin‐film infrared spectroscopy (XTFIS) shows pauses or slow stages, which are identified as static phases followed by dynamic phases with the incremental gain or loss of a helix turn. In addition, absorbance at 1637 cm^?1 suddenly increases at 82.1 s (30 % over 0.3 s), indicating a phase change and crystallization of the π‐helix, along with a coincidental decrease in the absorbance for the first π‐helix. A sharp peak occurs at the maximum of the phase change at 82.5 s, representing a pure NMT π‐helix. The spectra then undergo a decreasing general absorption loss over 150 s, with the π‐helix evolving further to an antiparallel β‐sheet fragment. The spectral quality arises from the immobilization of polar molecules on polar surfaces. The crystal structure is that of an antiparallel β‐sheet.     

Effect of diffusion and stresses on the magnetic properties of multilayer Fe/Pd and Fe/Ge films

Multilayer [Fe/Pd]₁₀ and [Fe/Ge]₁₀ films were studied using ferromagnetic resonance, magnetic-force and atomic-force microscopies, magneto-optical Kerr effect, and X-ray diffraction. It was shown that an increase in the interlayer thickness causes changes in magnetic parameters, such as the induced anisotropy, effective magnetization, coercive force, and the parameters of the fine magnetic structure. Reasons of the changes in the magnetic parameters were established.     

Evaluation of the efficiency of electrolysis in cells of various designs in inversion-voltammetric determination of lead

Efficiency of the stage of pre-electrolysis in inversion-voltammetric measurements was examined in relation to the hydrodynamic modes used.     

A rapid version of standardless stripping voltammetry for determining mercury in aqueous solutions

It was shown that mercury(II) in aqueous solutions can be determined by standardless stripping voltammetry based on the determination of the coulometric constant of the electrochemical cell. This approach considerably reduces the analysis time in comparison to the known analogs. The coulometric constants were found for electrochemical cells with a gold and a gold-graphite film electrodes in solutions of different volumes. The optimum time of preelectrolysis was determined for measurements using the proposed method.     

Simulation of nonstationary heat transfer in jacketed apparatus

Nonstationary heat transfer in jacketed apparatus was studied.