Dynamics of the Trapping of Microparticles by an Interference Field on Exposure to Continuous and Pulsed Radiation

The dynamics of motion of microparticles in a gradient light field depending on the acting radiation time sequences has been studied theoretically and experimentally. A water suspension of small polymeric balls illuminated by interference fringes of the radiation from a cw He–Ne laser ( = 632.8 nm) and also pulse-periodic YAG:Nd³⁺ laser ( = 532.1 nm; _p 17 nsec; f 50 Hz) was used. It has been established that the gradient field generated by continuous radiation ensures a higher velocity for transporting particles and, consequently, a more effective change in their local concentration and acceleration of their diffusion. In contrast to this, interference irradiation of particles by short repetitive pulses is not very effective for their transportation in space but ensures much higher instantaneous velocities and a higher kinetic energy. As applied to biological objects, this regime has a slight effect on the local concentration and diffusion of particles, but can cause conformational changes in biological structures.     

Experience with semi-conducting detectors

The paper describes silicon detectors with a deep surface potential barrier and their use in the spectrometry of charged particles.

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Finally, the authors would like to thank Ing. . imán and S. afrata, Candidate of Science, for their constant interest in our work and their support, as well as A. Irra for carefully preparing the silicon samples.     

Double phase-matched cascaded fifth harmonic generation in single nonlinear medium by focussed laser beam

Generation of a fifth harmonic by the cascading of two phase-matched third-order processes in a single centrosymmetric nonlinear medium with a focused fundamental beam is investigated theoretically. With the help of analytical and numerical investigations the optimized conditions for maximum conversion into the fifth harmonic are found. In general the optimal position of focusing depends on the values of the mismatches k₁ and k₂ for both steps of the third order cascading (++=3; 3++=5). It is shown that for best efficiency this method of fifth harmonic generation requires specially chosen k_1,opt and k_2,opt and focusing in the center of the nonlinear media. If the phase matching parameters are fixed and they deviate from the optimal values, then the optimal strength of focusing and position of the focus spot should be calculated according to the analysis presented here. PACS 42.65.-k; 42.65.Ky; 42.79.Nv     

Bose condensation,solitons and canonical transformations in quantum field theory

In an quantum sine-Gordon model in 1+1 dimensions, the condition that the vacuum expectation value of the Heisenberg scalar field reproduces static soliton solution to the classical equation is satisfied when the LSZ asymptotic quantum field undergoes a canonical transformation. This can be viewed as a quantum image of the Bäcklund transformation and the soliton is described in terms of condensation of quanta. Their confinement is ascribed to the non-implementability of unitary transformations among unitary inequivalent representations of the canonical commutation relations.Invited talk at the International Symposium Selected Topics in Quantum Field Theory and Mathematical Physics, Bechyn, Czechoslovakia, June 14–21, 1981.It is a pleasure to thank Professor J. Niederle and the Organizing Committee for the opportunity of participating in this Symposium and for the kind hospitality.     

An experiment to detect “empty” waves

An experiment has been conducted to test the speculation that empty waves suffer attenuation in their propagation relative to waves which carry singularities. This speculation leads to the prediction that the contrast of interference fringes should decrease exponentially with free independent path length. A double-slit experiment has been carried out in which the distance between the slits and the observation plane has been varied over a wide range. High contrast interference fringes have been recorded and the contrast measured as a function of distance between the slits and the observation plane. No convincing evidence is found for attentuated empty waves.     

Canonical path-integral quantization of yang-mills field theory with arbitrary external sources

Some modification of source terms is proposed for gauge field theories. In theSU(2) Yang-Mills theory with arbitrary external sources a canonical quantization procedure leads to a Lorentz-invariantS-matrix only when Fermi statistics is imposed on ghost fields. The usual source terms lead to a result that breaks Lorentz invariance and is singular when external chargesJskin0 vanish. The cases of the Abelian scalar electrodynamics and theSU(2) Yang-Mills field with external currents (Jskino=0,Jskini 0) are also discussed.     

Near Field Observation of a Refractive Index Grating and a Topographical Grating by an Optically-Trapped Gold Particle

We observed the near field for a refractive index grating fabricated on a planar light waveguide circuit (PLC) by scanning an optically-trapped 100 nm diameter gold particle. We demonstrate that stable trapping and scanning occur with a Gaussian laser beam at the scan velocity of 1.6 m/s and Nd:YAG laser power of 25mW. The scattered Ar laser light from the gold particle is strong at high refractive indexes of the grating with periods of 1.06 m and 0.53 m both by s and p polarized illumination. In addition, we observed the surface profile of the optical disk tracking groove with and without the gold particle. © 2004 The Optical Society of Japan     

Combined Fluorescence and NMR Studies of Reversed HPLC Stationary Phases with Different Ligand Chain Lengths

Alkyl chain bonded reversed HPLC phases consisting of 6 to 30 carbon atoms are investigated by fluorescence spectroscopy, steady-state and time-resolved fluorescence anisotropy, and solid-state NMR spectroscopy. The structure and dynamics of the interphase formed by alkyl chains and liquid phase penetrating each other are studied as a function of alkyl chain length. Increasing alkyl chain lengths lead to enhanced partitioning of the fluorescent probe diphenylhexatriene (DPH) into the interphase, as monitored by fluorescence decay curves. The concomitant spectral red shift of DPH fluorescence excitation maxima is evidence of increased interphase polarizability. Time-resolved fluorescence anisotropy measurements reveal that the motion of the probe molecule in the interphase is wobble in cone-like. Cone angles and rotational correlation times _R change from = 63° and _R = 0.75 ns in C₆ phases to = 42° and _R = 1.50 ns in C₃₀ phases, thus indicating decreasing probe mobility with increasing ligand length. This interpretation is supported by ¹³C CP/MAS NMR spectra, which show reduced contributions of alkyl chain gauche conformations, i.e., enhanced interphase order, in phases with long alkyl chains and high surface coverage. A concomitant increase in the line-widths of ¹H MAS NMR peaks indicates reduced mobility of the longer chains. The spectroscopic observations are consistent with the results of HPLC separations, where enhanced shape selectivity is found with increasing ligand length, rod-shaped molecules like DPH showing the greatest increase in retention time.     

Present status of electromagnetic interactions in light nuclei

Recent electron scattering experiments on the few-nucleon systems are presented. The interpretation of the data in terms of nucleon and meson degrees of freedom is discussed.Invited talk to the symposium Mesons and Light Nuclei IV, Bechyn, Czechoslovakia, September 5–10, 1988.     

CEMS Investigations of Fe-Silicide Phases Formed by the Method of Concentration Controlled Phase Selection

Conversion electron Mössbauer spectroscopy (CEMS) measurements have been made on Fe-silcide samples formed using the method of concentration controlled phase selection. To prepare the samples a 10 nm layer of Fe₃₀M₇₀ (M=Cr, Ni) was evaporated onto Si(100) surfaces, followed by evaporation of a 60 nm Fe layer. Diffusion of the Fe into the Si substrate and the formation of different Fe–Si phases was achieved by subjecting the evaporated samples to a series of heating stages, which consisted of (a) a 10 min anneal at 800°C plus etch of the residual surface layer, (b) a further 3 hr anneal at 800°C, (c) a 60 mJ excimer laser anneal to an energy density of 0.8 J/cm², and (d) a final 3 hr anneal at 800°C. CEMS measurements were used to track the Fe-silicide phases formed. The CEMS spectra consisted of doublets which, based on established hyperfine parameters, could be assigned to - or -FeSi₂ or cubic FeSi. The spectra showed that -FeSi₂ had formed already at the first annealing stage. Excimer laser annealing resulted in the formation of a phase with hyperfine parameters consistent with those of -FeSi₂. A further 3 hr anneal at 800°C resulted in complete reversal to the semiconducting -FeSi₂ phase.     

On the anisotropy of the FMR linewidth in iron-silicon single crystals

The ferromagnetic resonance linewidthH in in plane configuration was measured in single crystal discs of Fe-2·2% Si at frequency 36·14 GHz. Several methods of electrolytic and chemical polishing were used to minimize the effects of sample surface irregularities. By rotating the external field in the plane of the discs ((110) plane) the linewidth of well polished samples was found to be isotropic within the experimental errors (about 5%). Spurious anisotropy of linewidth was found in some imperfectly polished samples.     

Experimental test of the effective-photon hypothesis

The effective-photon hypothesis postulates a photon energy variable with light intensity according to a relation of the form =hv/[1– ₀ f(I)]=hv ₁ . This hypothesis has been subjected to direct experimental test. A Mach-Zehnder interferometer is illuminated with aQ-spoiled Nd:glass laser and the time history of the interference fringes is recorded with an image converter camera. The experimental results show that indeed the laser pulse is not monochromatic and that a large frequency change occurs with light intensity. In addition, the analysis of the results indicates that the principle of conservation of energy is not in contradiction with the hypothesis of effective photon, provided photons can exchange energy among themselves.     

Analysis of signal-to-noise ratio of the laser Doppler velocimeter

The signal-to-shot-noise ratio of the photocurrent of a laser Doppler anemometer is calculated as a function of the parameters which describe the system. It is found that the S/N is generally a growing function of receiver area, that few large particles are better than many small ones, and that generally the fringe or differential mode configuration is equal to, or better than, the reference beam mode.     

Evidence for the poisson distribution for quasi-energies in the quantum kicked-rotator model

A transformation on the two-dimensional torus which is related to the problem of limit distribution for the distance between the levels in the kicked-rotator model is considered. The first four moments of the r.w. which describe the numbers of visits of a point in a rectangle of measure are calculated. It is shown that when 0 they converge to the first four moments of a Poisson r.w.     

Contribution to the theory of single-mode laser modulation II. Conduction modulation

The problem of conduction modulation of laser radiation is considered. It is shown that acoustic wave interacting with photon field in active medium causes a periodic modulation of the number of quanta in the single-mode gas laser. The problem of modulation is solved quantum mechanically and it is shown that dielectric and conduction modulation give similar results.     

Fine structure of the emission spectrum of a single-mode injection laser. Nonlinear gain of active semiconducting medium

A theoretical analysis of single-mode emission of an injection laser is carried out in the framework of the nonlinear gain method. Nonlinear gain is regarded as the result of interaction of a strong (laser) field with weak fields having symmetrically detuned frequencies (superluminescent emission). The interaction is via beats in the inversion at the difference frequencies and correspondingly via a dynamic phase grating of the complex dielectric constant of the active region. Expressions are obtained for the spectral profile of the optical radiation in a single-mode laser with solitary diode cavity, and also in a laser with external cavity. An expression is obtained for the intensity-fluctuation spectrum in a single-mode laser with external cavity. It is shown that in such a laser the superluminescent modes adjacent to a laser mode are split into two components, each due to such an interaction.Notation a, b complex dimensionless coefficients of the eigenvector expansion of the field amplitudes - c velocity of light - D electric induction - E₀(z) laser-mode field amplitude on the cavity axis - E₁(z) complex amplitude of weak field of the long-wave spectral component - E₂(z) complex amplitude of weak field of the short-wave spectral component - E(x, y, z, t) total intensity of the light-wave field - f₁, f₂, f₃, f₄ functions characterizing the Fabry-Perot cavity - g_e total effective gain in diode cavity, including the mirror losses - g_m mode gain for the laser field - g₁, g₂ waveguide gains for the long- and short-wave components respectively - g₀ mode gain, saturated by the spontaneous emission, at laser field frequency - g nonlinear increment to mode gain - g_sp laser-mode gain deficit produced by spontaneous emission - G local value of the gain - G₀ laser-field threshold local gain - h₁, h₂ coefficients of expansion of the dipole amplitude in terms of the eigenvectors - photon energy - I() spectral density of laser-intensity fluctuations - J pumping rate - laser-diode length - L length of external part of the cavity - n refractive index - n^* group refractive index - N₀ threshold density of injected electrons - N density of injected electrons - N change of electron density - p() spectral density of the optical power of the radiation from the effective dipole - p() spectral density of laser optical power - P₀ threshold pump power - q₀=q₀+iq₀ complex constant of laser-mode propagation along the cavity axis - q₁=q₁+iq₁ complex propagation constant of the long-wave field component - q₂=q₂+iq₂ complex propagation constant of the short-wave field component - q change of real part of propagation constant due to change of field frequency by linear dispersion - q₁, q₂ increments to field propagation constants at the frequencies ₁ and ₂ with account taken of the gain and of the deviation of the dispersion from linearity - Q integral indicative of the effective cross section of the light flux - r diode-mirror reflection coefficient - R waveguide value of amplitude-phase coupling coefficient - s() effective-dipole spectral emission density - s_V() spontaneous-sources spectral density averaged over the diode volume - u₀(x, y) transverse distribution of laser-mode field - u₁(x, y) transverse distribution of long-wave field component - u₂(x, y) transverse distribution of short-wave field component - dimensionless coefficient indicative of the contribution of the spontaneous emission to one laser mode - _m=(1/)ln(1/r) diode-mirror losses - , dimensionless coefficients of the order of unity, indicative of the dependence of the mode and local gains on the electron density - total probability of electron recombination (with allowance for stimulated recombination) - ₁, ₂, ₃, ₄ effective complex propagation constants of the interacting fields - ₀(x,y,) complex dielectric constant - variation of dielectric constant - relative excess of pump above threshold - _e external quantum yield - () spectrally selective feedback coefficient of the external dispersive element of the cavity - ₀ value of () for corresponding to maximum reflection - ₁, ₂ eigenvalues of propagation constants - variations of propagation-constant eigenvalue - () spectral amplitude of effective dipole - _V() spectral amplitude of spontaneous sources averaged over the diode volume - electron spontaneous-recombination time - _p photon relaxation time - phase advance of laser field in the external part of the cavity - ₀ laser-field central frequency - ₁ frequency of long-wave component of the field - ₂ frequency of the short-wave component of the field - _g frequency corresponding to the m-th longitudinal resonance of the laser-diode cavity - difference frequency - ₀ relaxation-resonance frequency - _L spectral detuning of laser frequency from the diode longitudinal-resonance frequency - _R spectral distance between the laser frequency and the satellite peaks - _t spectral detuning of selective element from longitudinal resonance - _s width of selectivity profile of external reflecting element Optoelectronics Laboratory, Quantum Radiophysics Division, Lebedev Physics Institute, Academy of Sciences of the USSR. Translated from Preprint No. 108 of the Lebedev Physics Institute, Academy of Sciences of the USSR, 1989.     

Segregation of Components as a Result of High‐Power Laser Irradiation of Heterogeneous Condensed Media

The effects of periodic segregation of components in metastable (supercooled or supersaturated) binary alloys in the course of kinetic phase transformations as a result of laser irradiation of heterogeneous systems were studied analytically. Nonlinear processes of temporal and spatial selforganization of concentrationrelated structures were simulated using (i) a selfconsistent system of timedependent twodimensional equations for the distribution function for the sizes and spatial coordinates of the newphase particles and (ii) balance equations for the temperature and concentration of dissolved components; the latter equations account for nonlinearity of the particlesource function, sinks, for dependences of the phasetransition temperature on the surface curvature of particles and on the concentration of components, and for diffusive motion of particles in space. The domain of existence for the instabilities under consideration and the characteristics of the formed crystallizationrelated periodic structures are determined. It is established that nanoclusters formed during supersaturation of crystallizing material may play an important role in generation of selfoscillatory crystallization modes. Hydrodynamic aspects of liquidphase concentrationrelated stratification in heterogeneous systems based on immiscible components are considered.     

On the electromagnetic structure of elementary particles

Using modern similarity and dimensionality methods, criteria of similarity are derived and used as transformations, which effect the conversion from one natural system of units to another. The exclusion principles thus defined are used to determine the powers of the similarity criteria in quantitative relations.Systems of units of the fermion and boson types are used in the simplest identification of the parameters corresponding to elementary particles.A set of electric and magnetic physical constants with dimensionality length, area, and volume, is obtained and successfully unified within the limits of a vortex ring, the maximum dimensions of which are defined by the Compton wavelength, and the minimum by the classical radius of the particle. The vortex ring model is in accordance with the latest experimental data, and it enables the behavior of the incident and target particles in the scattering process to be predicted.In modern theoretical physics the elementary particles are still considered as essentially structureless point formations, and hence it is impossible to give a purely theoretical treatment of the structure of the particles. Thus the various attempts in this direction (Hofstadter, Blokhintsev) have a polyphenomenological character and are internally inconsistent. (The search for the structure of an elementary particle is carried out on the assumption that it is not elementary, since truly elementary particles are defined as point size.) The author recognizes the need for an original approach to the structure of elementary particles, based on a method of study adequate for the problem. Such a method is the theory of dimensionality and similarity (Sedov, Gukhman, and Kirpichev), which serves as a scientific basis of a physical experiment (Kirpichev), or as the scientific basis for a model of the phenomena, insofar as the criteria of similarity are a reflection of the physical model of the process (Gukhman).It is a pleasure to thank Academician L. I. Sedov and Professor K. A. Putilov for valuable criticism and advice, and Professor A. S. Irisov and V. V. Lokhin for useful discussions.     

Weyl quantization and metaplectic representation

The formal expansion defining the twisted exponential of an element of the Lie algebra _n ( ⁿ Sp(2, )) can be summed and this result is used to explicitly obtain the classical function u _t corresponding to an evolution operator associated to a quantum Hamiltonian belonging to the above mentioned Lie algebra.Then, by applying the Weyl quantization procedure to u _t we get a representation of the group W _n ( ⁿ Sp(2, )) in terms of integral operators, the kernels of which are expressed by means of the classical action. The family u _t being only locally defined, it must be considered as a distribution on the classical phase space in order to get the metaplectic representation.Membres du Centre National de la Recherche Scientifique.