The dynamic light scattering (DLS) technique was used for studying the processes of aggregation of spherical SiO2 particles in various diethylene glycol (DEG) suspensions. The suspensions were studied in a cuvette, in a millimeter-sized droplet and in a micrometer-sized droplet. For the first time DLS signals for droplets of picolitre volume, levitated in an electrodynamic quadrupole trap, were obtained. It is shown that the correlation analysis of light scattered from a micro-droplet allows monitoring the changes of its internal structure, as well as its motions: trap-constricted Brownian motions and random rotations.
In this paper we present progress in MOCVD growth of (100) HgCdTe epilayers achieved recently at the Institute of
Applied Physics, Military University of Technology and Vigo System S.A. It is shown that MOCVD technology is an
excellent tool in fabrication of different HgCdTe detector structures with a wide range of composition, donor/acceptor
doping and without post grown annealing.
Particular progress has been achieved in the growth of (100) HgCdTe epilayers for long wavelength infrared
photoconductors operated in HOT conditions. The (100) HgCdTe photoconductor optimized for 13-μm attain detectivity
equal to 6.5x109 Jones and therefore outperform its (111) counterpart.
The paper also presents technological progress in fabrication of MOCVD-grown (111) HgCdTe barrier detectors.
The barrier device performance is comparable with state-of-the-art of HgCdTe photodiodes. The detectivity of HgCdTe
detectors is close to the value marked HgCdTe photodiodes. Dark current densities are close to the values given by “Rule
07”.
Experimental elastic-scattering characteristics of single evaporating liquid microdroplet of solution and suspension are
reported. The microdroplets studied were composed of: (i) silica (SiO2) nanoparticles (225 nm radius) dispersed in
diethylene glycol (DEG) liquid suspension (ii) DEG and Sodium dodecyl sulfate (SDS) solution, and (iii) SiO2
nanoparticles dispersed in DEG and SDS solution. We observed regular Mie type fringes from (i), (ii) and (iii) at the
initial stages of the evaporation process followed by intensity fluctuations (speckles) for (i) and surface reflections
(blinking of scattered light intensities) for (ii) during the inclusions surface layer formation. For (iii), Mie-type fringes,
and a mixture of surface reflections (blinking of scattered light intensities) and intensity fluctuations (speckles) was
observed. The changes in the intensities and polarization of the scattered light showed characteristic stages of
evaporation driven processes occurring at the droplet surface. The observed phenomenon carry information about the
inclusions’ mean distances, size, and stages of aggregation of SiO2 nanoparticles and crystallization of SDS
nanocrystallites on the droplet surface. Additionally, we deposited samples of the final dried composite microobject on a
silicon substrate and analyzed with SEM. The study provide different surface diagnostic methods of configuration
changes in complex systems of nano-and microparticles evolving at the sub-wavelength scale and serves as an alternative
method for studying stages of droplet with submicron inclusions evaporation processes.
The examination of quality of the sperm ejaculate is one of the most important steps in artificial fertilization procedure. The main aim of semen storage centres is to characterise the best semen quality for fertilization. Reliable information about sperm motility is also one the most important parameters for in vitro laboratory procedures. There exist very expensive automated methods for semen analysis but they are unachievable for most of laboratories and semen storage centres. Motivation for this study is to elaborate a simple, cheap, objective and repeatable method for semen motility assessment. The method enables to detect even small changes in motility introduced by medical, physical or chemical factors. To test the reliability of the method we used cryopreserved bull semen from Lowicz Semen Storage Centre. The examined sperm specimen was warmed in water bath and then centrifuged. The best semen was collected by the swim-up technique and diluted to a proper concentration. Several semen concentrations and dilutions were tested in order to find the best probe parameters giving repeatable results. For semen visualization we used the phase-contrast microscope with a CCD camera. A PC computer was used to acquire and to analyse the data. The microscope table equipped with a microscope glass pool 0.7mm deep instead of some conventional plane microscope slides was stabilised at the temperature of 37°C. The main idea of our method is based on a numerical processing of the optical contrast of the sperm images which illustrates the dynamics of the sperm cells movement and on appropriate analysis of a grey scale level of the superimposed images. An elaborated numerical algorithm allows us to find the relative amount of motile sperm cells. The proposed method of sperm motility assessment seems to be objective and repeatable.
We re-examine the usual expectations for multipolar plasmon modes of a simple-metal sphere within a classical picture. We show that according to rigorous solution of the eigenvalue problem the complex eigenfrequencies of plasmon modes can be attributed to the sphere of size larger than the minimum size at given multipolarity the feature not known from widely used "low radius limit".
Evaporation of a droplet of pure water several micrometers in size was investigated. The droplet was levitated in an electrodynamic trap placed in a small climatic chamber. The evolution of the droplet and the evolution dynamics was studied by analyzing the coherent light scattering patterns with the aid of Mie theory. A numerical model of droplet evolution incorporating the kinetic effects near the droplet surface was constructed. By applying this model to the experimental data the mass and thermal accommodation coefficients were determined to be αC=0.12±0.02 and αT= 0.65±0.09. This model enabled to find the droplet temperature evolution and the relative humidity in the droplet vicinity with high precision as well.
We investigated elastic light scattering on isolated evaporating droplets of radius between 1 and 20 tim. The droplets were either pure water or a water based suspension they carried electric charge and were contained in an electrodynamic trap. The evolution of the trapped droplet was investigated by means of scatterometry. A numerical model of such evolution incorporating the kinetic effects near the droplet surface was constructed. For water droplets with spherical inclusions the radius as well as effective refractive index was determined. An essential deviation in the form of a resonance from predictions by standard effective medium theories was encountered. Simple analysis of the phenomenon was conducted and a qualitative explanation is proposed. Similar analysis was applied to fullerene water suspension droplets in order to investigate the real part of refraction index.
The dependence of the optical properties of large sodium clusters as a function of their size is studied. Clusters are light induced allowing observation of the smooth change of their sizes as a result of the spontaneous nucleation process. We combine the formalism of the classical Mie scattering theory for spheres of arbitrary large size and the concept of the collective electron oscillations (plasmons). The maxima in normalized intensities of light scattered by single cluster we attribute to resonant excitation of dipole and quadrupole plasmon oscillation respectively. We show that plasmon resonances take place for different cluster sizes when excited with different wavelength. We compare these results with expectations resulting from solving the problem of eigenfrequencies of free-electron sphere with the dielectric function described within the Lorentz-Drude model.
Laser light scattering by a drying droplet of water fullerene suspension several micrometers in size was studied. Two light wavelengths were used. The evolution of refractive index and radius of the droplet was investigated. Resonant scattering was identified and analyzed. Some conclusions were drawn on the microscopic properties of the suspension. Supplementing measurements of samples obtained by drying the water fullerene suspension and toluene solution were conducted with Atomic Force Microscope (AFM).
Water droplets of radius between 1 and 20 μm carrying electric charge were individually contained in an electrodynamic trap. The trap was kept in a small climatic chamber, which enabled imitating the temperature and humidity conditions of the lower troposphere. the sign of the charge of the droplet could also be controlled. for the humidity close to saturation, droplet injected into the trap was evaporating for a few seconds and could either undergo a Coulomb explosion and escape from the trap or stabilize at the size of a few μm. In such case the final droplet readius depended on the value of the droplet charge and of the humidity. The evolution of a trapped droplet was investigated by means of scatterometry. A numerical model of such evolution, incorporation the kinetc effects near the droplet surface was constructed. By fitting this model to the experimental data the evaporation coefficient was found to be 0.14±0.04 in average. Possibly a depend-ence of this coefficient upon the value of the droplet charge was found. An explanation of such dependence is suggested. The significant influence of the drople charge upon the evolution of small water droplets seems important for the detailed microphysical description of clouds.
Sodium clusters were produced in the stainless steel cell containing sodium vapors and helium, with the aid of the laser light resonant with the Na2 particles. The clusters formation was investigated. Data on the cluster size and dynamics were obtained. The theoretical model of clusters evolution based on the thermodynamics of the vapor-liquid transition was developed. The scattering of light on sodium clusters was studied and the theoretical formulas were fitted to the experimental data.
Sodium clusters were produced in the stainless steel cell with the aid of the laser light. As they did not exhibit any resultant velocity, mass spectrometry methods were not applicable. Optical scatterometry was find useful. The processes of cluster growth and decay were investigated as well as the spatial distribution of the density of clusters. Data on the cluster size and dynamics were obtained. The appearance of the acoustic shock wave after the rapid laser switch on was detected.
KEYWORDS: Light scattering, Sodium, Particles, Scattering, Temperature metrology, Laser scattering, Spectroscopy, Bessel functions, Polishing, Picture Archiving and Communication System
We report the observation of the size evolution of the laser light formed clusters. A cell containing sodium vapor
and the buffer gas (He) under high pressure was used in the experiment. Changes of the radius and of the density
of transient clusters were observed via the time evolution of the intensity of right-angle scattered light. The rate of
the cluster radius growth was found to vary from 0.012 to 0.1 pm/s.
PACS: 36.40.+d, 31.70.Hq, 64.70.-p.
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