Light-scattering intensity fluctuations in single aerosol particles during deliquescence

We use the deliquescence of single NaCl- and NaF-particles levitated in an electrodynamic trap to study light-scattering intensity fluctuations. During deliquescence the volume of the solid crystal and the liquid around it can be measured simultaneously with the light-scattering intensity. Such an experiment allows a comparison with numerical simulations of the intensity fluctuations in microdroplets containing inclusions. We find a power-law dependence proportional to the area of the inclusion for inclusions with radii approximately less than half in size of the total radius of the droplet. For larger inclusions this changes to a power law with a proportionality to the radius of the inclusion. A change of 30% in total radius does not change the intensity fluctuations. There seems to be no distinct difference in the behaviour of NaCl and NaF particles, even though the refractive index difference between solid inclusion and liquid host is 0.165 in the former and less than 0.009 in the latter. Furthermore, the fluctuation data of the pure NaCl deliquescence is applied to the ternary NaCl–CaCl₂–H₂O system and show good agreement with thermodynamic data.     

Long-lived luminescence of complex molecules

Results of investigations of all types of long-lived luminescence of organic molecules in the gas phase and condensed media are presented. Methods for identification and separation of contributions of phosphorescence and thermally activated fluorescence in long-lived luminescence of organic-molecule vapors are proposed. Energy transfer and migration processes in the case of the inductive-resonant mechanism of intermolecular interaction leading to the appearance of sensitized phosphorescence and annihilation-induced delayed fluorescence are considered. Experimental results on energy migration obtained for solid solutions of organic compounds are analyzed within the framework of the concepts of percolation theory with account for the microscopic inhomogeneity of the systems under investigation and the fractal properties of the clusters of activator molecules. Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, F. Skorina Ave., 70, Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 5, pp. 662–674, September–October, 1998.     

Effect of driving laser intensity fluctuations on optical bistability of a system with large permanent-dipole molecules

The statistical properties of an optical bistable system consisting of two-level atoms with large permanent dipole moments contained in a Fabry-Perot cavity are investigated assuming the external laser intensity fluctuations to be the main source of noise. The probability transformation rule is applied to obtain the probability distribution for the transmitted intensity whereas the probability distribution for the incident intensity is assumed to be that of the partially coherent laser light. It turns out that in the optical bistability region two values of fluctuation parameters are possible for a given value of input intensity, which produces interesting hysteresis effects.     

Bistability and intensity fluctuations in Zeeman lasers and amplifiers

It is shown that the fluctuation properties of certain Zeeman lasers and amplifiers are exhibit a sudden change when the coupling constant ξ is varied near ξ = 1. The possibility of a phase transition at ξ = 1 is discussed and fluctua properties both above and below this point are investigated using some previously derived equations for two-mode lasers.     

Oscilloscope display of picosecond fluctuations in light intensity

We report a new method for oscilloscope display of picosecond events in analogue form, using coherent pulse-expansion.     

Backscattering of stationary radiation in time-dependent random media: average intensity and intensity fluctuations

We consider backscattering of stationary radiation in a random medium whose wavespeed fluctuations depend on time and on space. We modify a previous derivation of the equations that govern the range-evolution of the spectra of the ensemble-averaged forward-and back-propagating components of the field and their second-order statistics, and extend the approach to treat the fourth-order statistics. The latter are governed by integro-difference equations that account for the broadening of the signal spectra due to the time-dependence of the random fluctuations. In the quasi-monochromatic regime, where spectra owing to a monochromatic excitation remain confined to a narrow band over extensive ranges, the integro-difference equations transform into ordinary differential equations that govern the time-dependence of the quantities of interest. We use this simplification to track the power fluxes and their fluctuations (scintillation) in a one-dimensionally stratified slab, where the wave-speed fluctuations depend on the range-coordinate normal to the planes of stratification, and also to treat modal propagation in a duct, where the wave-speed fluctuations depend on all three spatial dimensions. The results suggest that a Gaussian equilibrium is approached at large ranges, on a suitably defined backscattering scale that depends on the medium parameters and the geometry.     

Backscattering of stationary radiation in time-dependent random media: average intensity and intensity fluctuations

We consider backscattering of stationary radiation in a random medium whose wavespeed fluctuations depend on time and on space. We modify a previous derivation of the equations that govern the range-evolution of the spectra of the ensemble-averaged forward-and back-propagating components of the field and their second-order statistics, and extend the approach to treat the fourth-order statistics. The latter are governed by integro-difference equations that account for the broadening of the signal spectra due to the time-dependence of the random fluctuations. In the quasi-monochromatic regime, where spectra owing to a monochromatic excitation remain confined to a narrow band over extensive ranges, the integro-difference equations transform into ordinary differential equations that govern the time-dependence of the quantities of interest. We use this simplification to track the power fluxes and their fluctuations (scintillation) in a one-dimensionally stratified slab, where the wave-speed fluctuations depend on the range-coordinate normal to the planes of stratification, and also to treat modal propagation in a duct, where the wave-speed fluctuations depend on all three spatial dimensions. The results suggest that a Gaussian equilibrium is approached at large ranges, on a suitably defined backscattering scale that depends on the medium parameters and the geometry.     

Tagged particle fluctuations in uniform shear flow

The nonlinear Boltzmann and Boltzmann-Lorentz equations are used to describe the dynamics of a tagged particle in a nonequilibrium gas. For the special case of Maxwell molecules with uniform shear flow, an exact set of equations for the average position and velocity, and their fluctuations, is obtained. The results apply for arbitrary magnitude of the shear rate and include the effects of viscous heating. A generalization of Onsager's assumption of the regression of fluctuations is found to apply for the relationship between the equations for the average dynamics and those for the time correlation functions. The connection between fluctuations and dissipation is described by the equations for the equal-time correlation function. The source term in these equations indicates that the “noise” in this nonequilibrium state is qualitatively different from that in equilibrium, or even local equilibrium. These equations are solved to determine the velocity autocorrelation function as a function of the shear rate.     

空气介质阻挡放电单个微放电通道发光强度及振动激发温度的空间分布

通过清洗放电方法,在平行平板介质阻挡空气放电中得到了单个稳定的微放电通道（又称放电丝）.测量了从瞬时阳极到瞬时阴极单个放电丝的发光强度及振动激发温度的空间分布.研究表明：在外加电压的每半周中放电丝发光呈现杯型分布,杯底位于瞬时阴极处;振动温度在两平行板间隙的中心处最高而在瞬时阳极处最低. 关键词： 介质阻挡放电 微放电通道 振动温度     

Two-photon resonant Raman and luminescence of excitonic molecules in CuCl

Two-photon resonant Raman scattering via excitonic molecule in CuCl is studied with using dye laser excitation of different band widths. The yield of the Raman scattering is found to drop remarkably at resonant excitation and luminescence line of 0.3 meV half-width comes out. The predominance of the Raman or luminescence or their coexistence depends on the intensity and energy band width of excitation light.     

Energy fluctuations and particle emission in a crack mouth

Numerical estimates of the energy balance in a region lying in front of a main crack are made using classical mechanics and statistical physics and are illustrated through the example of cleavage of alkali halide crystals. It is found theoretically that emission of nanoparticles can occur in the course of dynamic fracture.     

Influence of some selected organic molecules on intensity of luminescence of TiO2:Eu electrodes

Eu³⁺ ions are anchored on TiO₂ matrix by coupling with 2,2′-bipyridyl 4,4′-dicarboxylic acid. Five different luminescence centers are observed for TiO₂|2,2′-bipyridyl 4,4′-dicarboxylic acid|Eu³⁺ electrodes due to electron transitions between d and f orbitals. Photo-luminescence of TiO₂|2,2′-bipyridyl 4,4′-dicarboxylic acid|Eu³⁺ electrodes is increased by attaching 2-thenoyltrifluoroacetone to Eu³⁺ ions. Immersion of TiO₂|2,2′-bipyridyl 4,4′-dicarboxylic acid|Eu³⁺|2-thenoyltrifluoroacetone electrodes in propylsulfide is found to be further increased intensities of luminescence bands by a factor of three.     

Sensitized fluorescence of dye molecules in polymeric matrices

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 48, No. 2, pp. 242–248, February, 1988.