Observation of intense stokes and anti-stokes lines in CH4 pumped by 355 nm of a Nd:YAG laser

The stimulated Raman scattering (SRS) and four-wave mixing (FWM) processes have been studied in detail in CH₄ gas pumped by the third-harmonic of Nd:YAG laser at =355 nm. The conversion efficiency and average output energy have been measured for the various Stokes and anti-Stokes lines at different experimental conditions. The threshold input energy at various CH₄ pressures has been calculated for the unguided and capillary waveguide Raman cells. The calculated values for the capillary case have been compared with the measured values at different CH₄ pressures and the two results are in good agreement.     

Numerical analysis of open circular longitudinally magnetized p-Ge and n-InSb waveguides

By means of coupled modes, there have been studied the dispersion dependencies of the main and three higher modes of open circular -gyrotropic waveguides made of semiconductor materials having electron or hole conductivity. Dispersion dependencies of such waveguides have been studied at various biasing magnetizing field inductions B and concentrations N of charge carriers. Cut-off frequency dependence on concentration N has been computed.     

EPR spectroscopy of poorly characterized systems: A historical and current view

Modeling of the CW-EPR spectra due to transition metal ions in non-crystalline systems grew in sophistication from the early 1960’s until fairly recently. A number of important effects have been introduced into the simulation of CW spectra over the past decade or so. These include allowance for local strain effects, the so-called “g-strain” and correlated “g-A strain”, the latter especially important in multifrequency spectroscopy. Limits have been reached in what is reasonable by way of guesses regarding the underlying lineshape function and further information can only be sought via ENDOR or ESEEM experiments in favourable cases. A clear understanding of the simplest way to describe field swept EPR via a master equation derived in the frequency domain will be reviewed in which asymmetric field swept lines sometimes occur naturally as a consequence of the theory. The paper will provide a review of the history of computer simulations and various statistical approaches to correlation effects covering examples as diverse as proteins and glasses. It is hoped that sufficient progress will have been achieved with a new Bruker ESP 380 pulsed spectrometer that some new results can also be reported.     

Production of slow singly charged fragments in 200 GeV/c hadron nucleus interactions

Measurements of slow, singly charged fragments in the target rapidity region have been performed for proton and pion induced reactions with various nuclei at 200 GeV/c. Multiplicity, angular and energy distributions are examined and used to study the effects of rescattering in the nuclear medium. Data are compared to a geometric cascade model and to simulations with the VENUS 3.11 and the FRITIOF 1.7 Monte Carlo codes.     

Propagation of waves through piezo-electric α-quartz crystals

Propagation of waves in piezo-electric -quartz crystals has been studied. The slowness surfaces and the wave surfaces have been derived. The wave surface has been found to contain cuspidal points which give directions of energy concentration.I take this opportunity to thank Dr. S. Das Gupta, for suggesting the investigation and for guiding me at various stages of the work.     

Determination of the Thermodynamic Characteristics of Complexes of Chlorosubstituted Anilines with Proton Acceptors

The influence of temperature on the spectral parameters of the absorption bands (NH) of free and hydrogen-bonded molecules of chlorosubstituted anilines with various proton acceptors in a CCl₄ medium has been studied in a temperature range of 290–330 K. The temperature dependence of the monomer–complex equilibrium constants has been investigated and the thermodynamic characteristics of the complexes have been calculated.     

Proton-neutron structure of collective excitations in 94Mo

Due to the recent development of radioactive beam production, various direct reaction studies in reversed kinematics have been made to investigate the behavior of the N = 20 shell closure in the neutron-rich region. Coulomb excitation, proton inelastic scattering, and fragmentation of unstable nuclei have been studied with γ-ray detection. Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002 RID="a" ID="a"e-mail: motobaya@rikkyo.ne.jp     

μSR research in semiconductors

Muon and muonium states in semiconductors especially silicon and germanium, have been the subject of SR research from the birth of the SR technique until the present. They are now under active investigation at at least three laboratories. Three different electronic states of the muon impurity have been firmly identified in silicon and more tentatively in germanium. This research has produced a significant amount of published literature which, due to the span of time and distance between the various experiments, shows large differences in technique, emphasis and style. I will attempt to present a coherent view of this literature distinghuishing the well-understood effects from those not understood.     

Disks vs. spheres: Contrasting properties of random packings

Collections of random packings of rigid disks and spheres have been generated by computer using a previously described concurrent algorithm. Particles begin as infinitesimal moving points, grow in size at a uniform rate, undergo energy-onconserving collisions, and eventually jam up. Periodic boundary conditions apply, and various numbers of particles have been considered (N2000 for disks,N8000 for spheres). The irregular disk packings thus formed are clearly polycrystalline with mean grain size dependent upon particle growth rate. By contrast, the sphere packings show a homogeneously amorphous texture substantially devoid of crystalline grains. This distinction strongly influences the respective results for packing pair correlation functions and for the distributions of particles by contact number. Rapidly grown disk packings display occasional vacancies within the crystalline grains; no comparable voids of such distinctive size have been found in the random sphere packings. Rattler particles free to move locally but imprisoned by jammed neighbors occur in both the disk and sphere packings.This paper is dedicated to Jerry Percus on the occasion of his 65th birthday.     

Polarizing properties of wire gratings in the long wave infrared

The parameters of wire gratings with various relationships between their period and the spacing of the wires have been studied experimentally. It is shown that a single grating with a period of 30 m and a wire diameter of 8 m polarizes not less than 92% of radiation in the 150–650 m wavelength range, while two such gratings polarize almost all the radiation in this range.     

A simple current pulsed low-pressure CO2 laser with passive Q-switching

We report on a simple and stable pulse tunable CO₂ laser suitable for many investigations in the region around 10m. The pulsed discharge when combined with the passiveQ-switching technique provides pulses of 100 ns duration with a peak power of few kilowatts.Due to the interest in pulsed low-pressure CO₂ lasers as useful irradiation sources, extensive investigations have been carried out. In particular, various Q-switching techniques have been developed to generate short CO₂ laser pulses [1–4].     

Dispersion characteristics of broadside coupled dielectric image guide at millimeter wave frequencies

Dispersion characteristics and wave impedance for the even and odd modes of the broad side coupled dielectric image guides are computed by using mode matching techniques. Dispersion curves for broadside image guide are plotted for various dielectric materials and dimensional parameters as a function of frequency. Normalized electric field for dominant electric field component E of TM even and odd modes for various half spacings between two dielectric slabs of broadside coupled image guide have been plotted. Polysterene ( r=2.56) and Stycast ( r=3.4) have been used as dielectric materials in fabricating broadside coupled image guide. This broadside coupled dielectric guide is very convenient as compared to the other dielectric guides. Since in case of broadside coupled image guide the dielectric slab can be bonded to the side metallic walls using some low loss adhesive material, while in other coupled dielectric guides the dielectric slab have to be supported by some low dielectric constant material (Eccofoam with r=1.02) to maintain the proper distance of side metallic walls from the dielectric slab. Since this structure is symmetrical, this configuration can be analysed in terms of even and odd mode phase velocities. The difference in these even and off mode phase velocities can be used to determine the coupling between coupled dielectric slab. Various couplers in this configuration can be realised.     

Superliquid state of an exciton mixture with small exciton radii in molecular crystals

The energy spectrum of excitons with a small radius in a superliquid state in molecular crystals has been investigated. A more complicated structure of the exciton energy spectrum with a number of equivalent minima for k 0 has been considered. The problem was solved as that of determining the energy spectrum of a mixture of various types of non-ideal exciton gases in a superliquid state, corresponding to the individual exciton energy minima. The appropriate branches of the energy spectrum of elementary excitations (hydrons) have been determined and the conditions for their stability have been investigated.     

20 years of J/\psi suppression at the CERN SPS

J/ suppression was predicted to be a signature of deconfinement and has been extensively studied at the CERN-SPS in proton, light and heavy ion induced reactions. Indeed, proton, O, S and Pb ion beams, at various incident energies, have been used at CERN on different targets, in order to precisely quantify J/ production as a function of both the colliding nuclei and the centrality of the collision itself. This paper reviews the results obtained so far with a critical discussion of the experimental conditions and successive improvements implemented for the various data samples. It makes a tentative summary of what has been learned on the subject, from the experimental point of view, in the SPS energy range.Arrival of the final proofs: 7 July 2005PACS: 25.75.-q, 25.75.Nq, 13.20.Gd     

Model for cometary grains to explain optical polarization

The observed optical polarizations for comets have been explained in past assuming cometary grains to be compact spheres, such that Mie theory could be applied to simulate the observed polarizations. However, recently other shapes like spheroids and then more realistic shapes like aggregates of monomers have been considered for cometary grains, to explain the observed polarizations. For this purpose T-matrix or DDA based light scattering technique was mostly used to simulate the observed polarizations. A number of authors have used T-matrix, DDA and various other techniques along with aggregate grain model to explain the polarizations of comets like 1P/Halley, C 1995/O1 Hale-Bopp, C/1990 K1 (Levy) and C/1996 B2 Hyakutake, etc. Recent STARDUST mission had suggested cometary grains to be mixtures of compact and porous aggregates. Accordingly, attempts have been made recently to reproduce the cometary polarization with mixtures of various compositions, shapes and porosity.The work presented here considers a model for cometary grains which contains (1) solid grains of pyroxene (silicate) and organic with various sizes of spheres, prolates and oblates and (2) aggregates with monomers of various sizes, with composition of pyroxene (silicate) and organic, having structures (shapes) defined by BCCA and BAM2 codes. It was found that the present model can explain the observed polarization data, especially the negative branch, for comet 1P/Halley at , more effectively as compared to other work done in past. Among the aggregates the BAM2 structure was found to play a key role, in deciding the cross-over angle and depth of negative polarization branch.     

Control and precise measurement of carrier-envelope phase dynamics

The evolution of the carrier-envelope offset phase _CEO of a 10-fs Ti:Sapphire laser has been traced on time scales from microseconds to seconds using various techniques. Precise locking of this phase has been achieved down to an rms deviation of 1/40 of an optical cycle. Stability measurements have been performed independently of the feedback loop, focusing on the phase jitter introduced by the feedback loop itself, the pump laser, and a prism compressor. It is shown that a multi-mode pump laser introduces more phase noise on _CEO than a single-mode pump laser. PACS 42.65.Re; 42.60.Mi; 42.62.Eh     

The temperature dependence of the deformation strength of solid Cu-Al solutions

The temperature dependence of the deformation strength, of the parameters ₀ and K of Pötsch's equation, and of the discontinuous deformation in solid Cu-Al solutions of various concentrations have been studied. It was shown that the temperature dependence of and ₀ changes substantially when the alloy concentration is increased (under otherwise equal conditions). The nature of the processes which lead to the disappearance of the deformation discontinuity and to a sharp high-temperature recrystallization by process annealing is discussed.     

Diffusion studies

Mössbauer spectroscopy represents a unique method to determine the frequency and the vector of diffusion jumps in solids. The elementary diffusion event can thus be studied in a microscopic way. In order to get maximum information experiments have to be performed on single crystals.Mössbauer studies of long-range diffusion, on the one hand, have proved the reliability of the method but also demonstrated the considerable technical effort which is necessary. Investigations of localized diffusion (diffusion in a cage), on the other hand, have been successful in various fields of physics and biophysics.     

Certain exact methods in the theory of nonlinear waves

Conclusions In this short lecture we have expounded only a portion of the methods that have currently been developed for finding exact solutions of problems in the nonlinear theory of waves. They have been used for an exact solution of a large number of model equations, although, as has already been noted, the derivation of these equations is frequently approximate [3, 83]. Numerous publications are currently, as is evident from the bibliography, devoted mainly to proof of the applicability of various approaches to equations that have already been studied and to the application of a definite methodological generality. However, the number of equations of interest for application purposes that have been solved exactly is for the time being increasing slowly. It may be hoped that familiarity with new ideas in this field will lead to a noticeable increase in the number of solvable equations. The joint application of exact, approximate and numerical methods (which Zabusky has combined in the term synenergetic approach [84]) will allow a significant advance in the understanding of the general picture of wave processes in nonlinear dispersive media.Scientific-Research Institute of Radio Physics. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 19, No. 6, pp. 883–901, June, 1976.