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Vol 46, No 6 (2019)
- Year: 2019
- Articles: 6
- URL: https://journal-vniispk.ru/1068-3356/issue/view/14162
Article
187-190
Significant Decrease in the Breakdown Threshold Voltage of the Commercial Laser Flash Lamp under kHz Pumping
Abstract
For the first time, to our knowledge, a multiple (to a factor of 3) reduction of the breakdown threshold of commercial cylindrical laser flash lamps with capacitive (through lamp electrodes) high-frequency (HF) pumping (19-3000 kHz) in comparison with a DC breakdown threshold is observed. When operating at a frequency of 400 kHz, a proportional decrease in the HF breakdown threshold is detected for a twofold increase in the relative dielectric permittivity ε when air as a cooling agent (ε = 1) is replaced by capacitor oil (ε = 2). An increase in ε to 21 in acetone is accompanied by a 30% decrease in the breakdown threshold and its subsequent stabilization with an increase in ε to 81 (in water). It is found that the breakdown threshold dispersion has two stages: an abrupt drop with a high (0.1–0.2 kV/kHz) slope in the range of 0–19 kHz and a smooth (~30%) decrease with increasing frequency to 3000 kHz.
191-196
Features of the Microstructure of the Surface Region of the Photoelectric Converter with a Porous Silicon Antireflection Film and an n+-p Junction Formed by Laser Radiation
Abstract
The microstructure of the surface region of the silicon photoelectric converter with an n+-p junction and an antireflection porous silicon film is studied by scanning electron microscopy and Raman spectroscopy methods. The n+-p junction was formed by laser irradiation of the surface of a porous silicon film containing a phosphorus impurity. It is shown that laser irradiation causes partial recrystallization of the porous silicon film and the n+-p junction formation within silicon crystallites.
197-200
Photoinduced Orientational Structure Transformation in Cholesteric Microdroplets
Abstract
In this study, the photoinduced orientational transitions at the variation of boundary conditions in the droplets of cholesteric (chiral nematic) liquid crystal are obtained and investigated. The effect is caused by photoisomerization of the azobenzene dendrimer additive dissolved in the liquid crystal and adsorbed on its interface. A sequence of orientational transitions under low-intensity (~1 mW/cm2) ultraviolet irradiation is revealed.
201-205
From the Coulomb to Effective Interaction: Application to Bose—Einstein Condensation
Abstract
An expression for the short-range effective interaction potential of “quasinuclei” is derived based on the “pure” Coulomb interaction model. This model represents the equilibrium Coulomb system (CS) of interacting electrons and identical nuclei using the adiabatic approximation for nuclei and an arbitrarily strong (in general) interaction for the electronic subsystem (degenerate or nondegenerate). Based on general properties of the Coulomb interaction, it is shown that the Fourier component of the effective pair potential between “quasinuclei” is discontinuous at the wave vector q = 0 in the case of the weak interaction between electronic and nuclear subsystems. This discontinuity is important for Bose-condensed systems such as Hell and rarefied alkali-metal gases at temperatures lower than that of the Bose condensation transition when a macroscopic number of quasiparticles with momentum q = 0 exist. It is shown that there can be a spectral gap for single-particle excitations, which disappears in the normal state.
206-209
Nonlinear Refraction in Colloidal Ag2S Quantum Dots
Abstract
Features of nonlinear refraction formation in colloidal solutions containing Ag2S quantum dots passivated with thioglycolic acid (Ag2S/TGA QDs) with a concentration of 0.1% and an average size of 2.0 nm are considered. Nonthermal self-focusing caused by the “band filling” effect under exciton excitation was detected by the Z-scanning method for 10-ns pulses of a YAG:Nd laser at a wavelength of 532 nm for Ag2S/TGA QDs having an exciton absorption maximum at 590 nm.
210-214