Raman Scattering Enhancement Based on High-Pressure High-Temperature Diamonds†

Journal of Russian Laser Research - We discuss the use of high-pressure high-temperature (HPHT) diamonds for the determination of trace amounts of various Raman active substances. The amount of the...     

Motion of a variable-volume sphere in an ideal fluid near a plane surface

The motion of a spherical cavity in a fluid is investigated. The radius of the sphere varies under the action of a constant pressure at infinity. The problems of the collapse of a cavity moving in an unbounded fluid and of the collapse of a cavity near a plane are solved in the exact formulation. The occurrence of an initial translational velocity or the presence of a solid surface, by contrast with the collapse of a sphere at rest in an unbounded fluid [1], yields a limiting radius at which the process of collapse ceases. A sphere initially at rest near a plane always comes into contact with the plane as a result of collapse. The radius and velocities at which the sphere arrives the plane are calculated for various initial distances from the latter. The possible mechanism of the action of a cavitation bubble on a solid surface is discussed.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 94–103, September–October, 1971.     

Motion and filling of cavities in a boundless liquid and close to a plane

The motion of bubbles in liquids has been studied in many earlier papers [1–8]. In this paper methods of the projection type are applied to the problem of a cavity in an ideal, incompressible liquid in the absence of vortices. The collapse of a bubble having a finite initial velocity in a boundless liquid is considered; also considered is the collapse of a stationary bubble close to a solid wall. Using the small-parameter method the generation of a jet is examined analytically. A numerical computing method not involving small parameters is developed; it is based on calculating the projection by numerical computation of the corresponding integrals. The method combines economy and simplicity of application with a high accuracy in the region in which the representation of the velocity potential by a series of spherical functions remains effective.     

Transfer of energy from an evaporating drop in a vapor medium

The article considers the temperature distribution around an evaporating drop in a vapor medium. The transfer of energy is effected by molecular thermal conductivity, convection, and radiation. The mean length of the free flight path of the radiation considerably exceeds the characteristic distance at which the temperature changes. The times required for relaxation of the temperature to a steady-state value are determined, as well as the characteristic distances at which the temperature distribution changes.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 1, pp. 74–78, January–February, 1972.The authors thank V. G. Levich for his evaluation of the results obtained.     

Application of the Pulsed-Neutron Method for Measuring the Reactivity of the Fissile Systems with Reflector

The experiments on recording the radiation decay signal of the GIR2 reactor core in the range from 0 to 40 µs when exposed to an external intense neutron pulse with a duration of ∼1 µs are performed. The reactivity interval from subcritical (−7.5 β) to critical (+0.28 β) states of the reactor is studied. It is found that the signal of the detector with a plastic scintillator depends on the reactivity and is proportional to the change in the density of thermalized neutrons in the reactor converter. The results show that the reactivity of the GIR2 reactor can be determined on the basis of measurement of the signal decay of a scintillation detector and the well-known expression $${\alpha _\infty } = {\beta \over \Lambda }(\rho - 1)$$ to calculate the reactivity values only for states with a reactivity greater than ∼−3 β.     

Stimulated Raman scattering in light and heavy water under picosecond laser excitation

The spectra of stimulated Raman scattering in ordinary and heavy water under excitation by second harmonic of a picosecond Nd:YAG laser were compared. It was shown that when stimulated Raman scattering is excited in water in cavities of a photonic crystal (synthetic opal matrix constructed of silica nanoglobules) or a photonic glass in the form of close-packed monodimensional millimeter-size amorphous-quartz balls, the efficiency of stimulated Raman scattering increases significantly compared to a uniform liquid medium.     

Photoluminescence of supernatant liquid of washed erythrocytes upon ultraviolet excitation

In this paper, we present the results of the study of supernatant liquid of washed erythrocytes by the photoluminescence upon ultraviolet excitation. The spectra of intrinsic photoluminescence of an aqueous solution of “Sodium adenosine triphosphate-Vial” (Na₂ATP) were compared with the spectra of supernatant liquid of erythrocytes with added Na₂ATP, glucose, and without additional substances. The results of the comparison suggest that ATP emerging from washed erythrocytes into environment can be recorded in supernatant liquid.     

Probe Raman spectroscopy of sodium uranyl-acetate microcrystals

The technique for recording Raman spectra in uranium compounds using a probe minispectrometer with a multielement radiation detector has been developed. A selective filter, which reflects exciting laser radiation and transmits Raman signals, has been used to suppress the exciting radiation. It is shown that the technique developed makes it possible to record Raman spectra from a small amount (~10^–5 g) of sodium uranyl-acetate polycrystals in a wide spectral range for several seconds.     

Splash type mass transfer on the water film at downflow and upflow

Generation of droplets on a surface of the water thin film at upflow and down flow is considered. Expressions for computation of splash type mass transfer were developed.