Detection of nitrogen dioxide by means of a gold film in a surface-plasmon resonance scheme

It is demonstrated that nitrogen dioxide can be detected by means of a gold film in a surface-plasmon resonance scheme. The sensor response is reversible at room temperature and permits detection of nitrogen dioxide down to concentrations of the order of 1 ppm. Pis’ma Zh. Tekh. Fiz. 23, 46–51 (December 12, 1997)     

Application of a nuclear quadrupole resonance method to measure stress in a matrix-tracer system in composites

A quantitative correlation has been established between the shift of the nuclear quadrupole resonance frequency of the tracer and the stress in a matrix-tracer system in composites. Measurements are made of the ⁶³Cu resonance frequencies in samples of epoxy resin containing cuprous oxide powder. The stresses in the resin and their dependences on temperature and external pressure are determined. Pis’ma Zh. Tekh. Fiz. 23, 14–18 (April 12, 1997)     

Plasma parameters of an electron cyclotron resonance discharge in a magnetic mirror in a quasi-gasdynamic confinement regime

An experimental investigation is made of x-ray bremsstrahlung in the 2–10 keV range of a pulsed discharge under electron cyclotron resonance conditions in a straight magnetic mirror system pumped by a high-power millimeter radiation beam. The plasma temperature and density were determined from the spectrum and intensity of the x-rays. The results indicate that a quasi-gasdynamic plasma confinement regime is achieved. Pis’ma Zh. Tekh. Fiz. 25, 90–93 (July 26, 1999)     

Hyperfine structure of magnetic-resonance electrical conductivity of doped polydiacetylene

Magnetic resonance with a hyperfine structure which can be detected from the electrical conductivity has been observed in iodine-doped polydiacetylene films. This resonance is attributable to transitions between Zeeman levels in the spin-dependent carrier transfer process in a system of localized paramagnetic centers. Pis’ma Zh. Tekh. Fiz. 25, 86–90 (December 12, 1999)     

Generation of electromagnetic waves by electrons rotating in a radial electrostatic field in free space

A theoretical analysis is made of mechanisms for the generation of electromagnetic waves by electrons rotating in a radial electrostatic field formed by a positively charged filament in free space. A dispersion equation is obtained to describe the interaction between the waves and nonrelativistic electrons. It is shown that electromagnetic fields can be generated by means of Čerenkov resonance. The frequencies and growth rates of the emitted waves are determined and their dependence on the parameters of the problem is investigated. Pis’ma Zh. Tekh. Fiz. 25, 1–4 (November 12, 1999)     

Conversion of the polarization of an electromagnetic wave under cyclotron resonance in a two-dimensional electron system

A theoretical analysis is made of the conversion of the polarization of an electromagnetic wave when cyclotron resonance is excited in a two-dimensional electron system. It is shown that the greatest conversion of the polarization can be achieved in the reflected wave. At high electron concentrations the effect remains very appreciable even in the presence of electron scattering. In this case, the wave polarization conversion effect can be used to obtain information on electron relaxation in a two-dimensional system. Pis’ma Zh. Tekh. Fiz. 25, 21–26 (November 12, 1999)     

Nonequilibrium surface ionization of water molecules in a high electric field in the presence of resonance absorption of near-infrared radiation

The results of experiments undertaken to establish the connection between the current of ions desorbed from the surface in the presence of an electric field and the frequency of the infrared radiation incident on that surface are described. It is shown that resonance absorption of infrared radiation by adsorbed molecules increases the efficiency of the surface ionization process. Pis’ma Zh. Tekh. Fiz. 23, 22–25 (December 12, 1997)     

Active microwave pulse compressor utilizing an axisymmetric mode of a circular waveguide

A novel active microwave pulse compressor in the form of an axisymmetric cavity is implemented and investigated. The cavity is formed by: a) a Bragg reflector, b) a cylindrical section, and c) an output resonance reflector in the form of an electrically controlled gas-filled spark gap. The compressor is excited by the TE₀₁ mode of a circular waveguide at a frequency of 9.4 GHz. Working at atmospheric pressure, the compressor produces output pulses with a power of 1.8 MW and duration 25 ns at a compression coefficient of around 20. Pis’ma Zh. Tekh. Fiz. 24, 6–11 (October 26, 1998)     

Simultaneous measurement of temperature and pressure

It is shown theoretically and experimentally that nuclear quadrupole resonance can be used to measure temperature and pressure simultaneously. Pis’ma Zh. Tekh. Fiz. 24, 54–57 (January 26, 1998)     

Indication of the presence or absence of convective motion in water by nuclear magnetic resonance

Nuclear magnetic resonance was used to determine the characteristic parameters for the evolution of an ensemble of gas bubbles in a liquid exposed to microwave irradiation. These parameters can be used to determine whether convective motion takes place in the liquid. It is observed that a liquid may be “strengthened” by low-intensity radio waves. Pis’ma Zh. Tekh. Fiz. 24, 87–90 (September 26, 1998)     

Polarization Effect in ESR of Co Doped CuGeO<Subscript>3</Subscript>

Electron spin resonance of a single crystal of CuGeO₃ doped with 2% of Co has been studied at f = 99 GHz in temperature range 1.8–50 K. Contributions to ESR absorption from Cu²⁺ chains and from Co²⁺ ions were derived. It is found that functions obtained for ESR integrated intensities: Curie-Weiss for Cu²⁺ (χCu ∼ C _Cu/(T + Θ), with Θ = 92 K) and Curie for Co²⁺ (χCo ∼ C _Co/T) are well consistent with temperature dependence of static magnetic susceptibility. Strong dependence of ESR absorption on polarization of oscillating magnetic field was discovered for Co²⁺ contribution. Polarization effect was studied for magnetic field applied along a, b and c directions. Values of g-factors of resonance lines are presented.     

Nutational nuclear quadrupole resonance in metal oxide compounds of copper

A pulsed nuclear quadrupole resonance method that can be used to study compounds with broad lines, especially metal oxide compounds of copper, is considered for the first time. Pis’ma Zh. Tekh. Fiz. 25, 74–77 (June 12, 1999)     

The effect of internal reflections of the field on the parameters of a superradiant pulse

Superadiation (SR) of an inverted two-level medium, described by one-dimensional Maxwell-Bloch equations without assuming that the amplitudes of the electric field vary smoothly along the sample, is studied. It is shown that as the initial inversion density increases, a transition is observed from the so-called “lethargic” field amplification regime, characteristic for the initial stage of SR, to a regime close to the ordinary exponential law. This accelerates the process and can lead to synchronization of counterpropagating SR pulses. Estimates are obtained for the average value of the delays of the oppositely propagating pulses and for their correlation criterion, which depends strongly on the ratio of the sample length and the half-wavelength of the resonance radiation. The possibility of realizing SR under conditions of strong phase relaxation of the active medium is discussed. Pis’ma Zh. Tekh. Fiz. 25, 24–31 (October 12, 1999)     

Determination of the average size and concentration of air bubbles in water by nuclear magnetic resonance

Nuclear magnetic resonance has been used to determine the mean radius of air bubbles in distilled water that has stood for a long time and the volume concentration of these “reduced to mean radius” bubbles. It is shown that the kinetics of the change in the concentration of these bubbles can be observed from the change in the spin-spin relaxation time. Pis’ma Zh. Tekh. Fiz. 23, 42–45 (July 12, 1997)     

New properties created in metal-oxide-silicon structures by reducing their dimensional parameters to the nanometer range

An experiment has been carried out in which standard metal-oxide-silicon barrier structures are used to develop resonance tunneling of electrons. The result is an extension in the array of properties of the structure. In particular, the capacitance-voltage characteristics take on resonance features: steps and peaks in one range of applied voltage and the classical behavior in another. The number of resonance features can be controlled by the applied voltage. Hysteresis observed in the capacitance-voltage characteristics indicates that the structure is multistable, that it has the property of memory, that electron charge can be written and erased. Pis’ma Zh. Tekh. Fiz. 23, 71–76 (February 26, 1997)     

Broadening of the particle resonance drift trajectory and tritium injection into a fusion reactor with an I=3 helical winding

Two fusion reactor problems, removal of helium ash and fuel (tritium) injection, can be solved using the concept of “drift island motion.” The motion of a drift island is an indicator of the broadening of the resonant trajectory of a charged particle guiding center. This trajectory broadening occurs if two conditions are satisfied. First, the drift pitch angle of the particle is equal to the resonance values i*=n/m, where n and m are the “wave numbers” of the perturbing magnetic field. Second, the drift pitch angle i*=n/m “moves” over the plasma cross section as the particle moves. This displacement is caused by a slow change in the helical magnetic field with time as the particle moves. It is shown that this effect may occur in a fusion reactor with an l=3 helical winding and may be used for tritium ion injection. Pis’ma Zh. Tekh. Fiz. 25, 5–13 (January 26, 1999)     

Simulation of impact-induced generation of hypersonic phonons and the resonance principle of activation of the compaction of nanopowders

Computer simulation is used to study the generation of induced hypersonic phonon oscillations at the instant of impact of α-Fe nanoparticles. A principle is proposed for the resonance amplification of these oscillations and the activation of the compaction of the nanoparticles by means of selective ultrasonic/hypersonic action or infrared/microwave radiation synchronous with the impact. Pis’ma Zh. Tekh. Fiz. 23, 81–88 (June 26, 1997)     

Growth of cubic GaN by molecular-beam epitaxy on porous GaAs substrates

It is shown that GaN layers can be grown on (100)-and (111)-oriented porous single-crystal GaAs substrates by molecular-beam epitaxy with plasma activation of the nitrogen by an rf electron cyclotron resonance discharge. The resulting undoped epitaxial layers possessed ntype conductivity with a carrier concentration ∼10¹⁸. Data obtained by scanning electron microscopy and cathodoluminescence indicate that at thicknesses ∼2000 Å, continuous layers of the cubic GaN modification are obtained regardless of the substrate orientation. Pis’ma Zh. Tekh. Fiz. 25, 3–9 (January 12, 1999)     

Resonance ring interferometry with incoherent light

A new method of measuring the phase nonreciprocity in a passive ring resonator using a light source of low coherence is described. The method provides effective suppression of noise from the backscattering of light in the ring resonator and insensitivity of the interferometer to excursions of the resonance frequencies of the resonator due to reciprocal effects (e.g., thermal expansion) and also permits modulation and compensation of the phase nonreciprocity by using a device outside the resonator to shift the frequency of the light. One version of a low-coherent resonance ring interferometer is examined, viz., a two-transit asymmetric interferometer with a rotating mirror. Pis’ma Zh. Tekh. Fiz. 24, 24–29 (September 12, 1998)     

Photoresonant ionization of gaseous media by excimer laser radiation

An identification is made of twenty five elements whose resonance lines overlap the emission lines of high-power pulsed ultraviolet gas lasers or lie in the immediate vicinity of them, so that the mechanism laser ionization based on resonance saturation (LIBORS) can be used to ionize the vapor of these elements. Resonance transitions of atoms and ions excited by the same laser (by krypton fluoride and xenon fluoride lasers, respectively) are observed for tantalum and uranium. It ishas been suggested that these elements may be used as “catalysts” for “ catalytic” resonance ionization (CATRION) of dense multicomponent gas mixtures. Experiments have been carried out to study the krypton fluoride laser irradiation of expanding vapor clouds of different elemental composition, created by the evaporation of targets with a ruby laser. Photographs obtained with an image converter, measurements of the refractive index gradient from the deflection of the laser beam, as well as probe and spectroscopic measurements indicate that the clouds undergo photoresonant ionization if they contain tantalum vapor but that the laser radiation has no influence otherwise. Pis’ma Zh. Tekh. Fiz. 23, 24–32 (May 12, 1997)