Radiation Scattering under Laser Irradiation of a Target Blown by a Two-Phase Stream

We have investigated the spectral characteristics of scattered radiation ( = 0.69 m and = 1.06 m) under probing laser action (q = 10³ W/cm²) on a textolite target of streamline shape blown by a cold two-phase stream (with talc and black particles). By the measured transverse scattering indicatrices the dependences of the scattered radiation intensity on the probing angles and the sort of particles and their number density in the stream have been established. The relative contributions of particles of the stream and the target surface to the total scattering by the target–two-phase-stream system have been determined.     

Scattering of Radiation of the Sun and the Sky from Two Dimensional Rough Sea Surfaces

The scattering of optical wave from two dimensional rough sea surfaces is studied first with method of facets. The sea surface is divided into many facets, and each facet is treated as a surface with small roughness instead of a smooth plane, therefore more practical and effective. In addition the shadowing function of sea surfaces for arbitrary incident and scattering angles is numerically calculated with the Z-BUFFER method, which applies to any kinks of rough surfaces compared with the methods available. Finally the spectral irradiance of the sun and the spectral radiance of the sky for different time at sea level with fine weather are obtained with the software of Lowtran7, and the scattering of the radiation of the sun and the sky from two dimensional rough sea surfaces for different time, waveband and wind speed is studied, which is of great reference value for reducing the interference to the infrared detector due to the scattering of the radiation of the sun and the sky from sea surfaces.     

Spin fluctuations in both the ordered and paramagnetic phases of MnSi! MnSi a heavy Fermi liquid?

Polarised neutrons and polarisation analysis have been used to determine the diffuse magnetic scattering from MnSi as a function of temperature. Measurements at 50 K (1.72T _c) and 100 K (3.45T _c) in the paramagnetic phase confirmed the presence of strong spatial correlations previously reported at 300 K (10T _c) and 580 K (20T _c). The spatial correlations between regions of spin density separated by 12 Å are of a ferromagnetic nature and determine the static susceptibility. Integration of the paramagnetic response over an inverse atomic volume yields a moment per manganese atom of 1.2 _B , a value considerably larger than the 0.4 _B observed in Bragg scattering and magnetisation measurements at 4.2 K. Measurements made at 11 K in the ordered magnetic phase reveal strong diffuse scattering corresponding to 0.8 _B per Mn atom. The increase in the diffuse scattering observed in the paramagnetic phase corresponds to the passage of the Bragg component into the background.The presence of significant scattering in the ordered phase and the very unusual wave vector dependence of the diffuse scattering observed at 11 K has been interpreted assuming MnSi to be a heavy Fermi liquid. Furthermore we believe these measurements give the first direct observation of the exchange hole.     

Bistatic scattering by arbitrarily shaped objects with rough surface at optical and infrared frequencies

The scattering cross sections for arbitrarily shaped dielectric objects with rough surface are determined for optical and infrared frequencies using the Kirchhoff approximation. The formula of the coherent scattering cross section is derived, and numerical method of incoherent scattering cross section is given. As a specific example, the infrared laser scattering cross sections of rough spheres are calculated at 1.06 m.     

Resonance interaction of antineutrinos with electrons

Expressions are given for the cross sections of the processes v_ee v and v_ee v _e ^' e' from the viewpoint of the hypothesis of weak interactions via intermediary vector mesons taking separate account of the polarizations of the electron target and the muon (electron) emission. An analysis is given of the cross sections of processes which are admissible according to both the two- and four-component theories of the neutrino. The degree of longitudinal polarization of meson emission is also determined for the interaction of incident antineutrinos (neutrinos) with a polarized target in the processes ve v, ve⁺ v⁺.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 6, pp. 48–53, June, 1971.The author is grateful to B. K. Kerimov for his useful advice which stimulated the appearance of this work and also to Yu. M. Kasumov for his constant assistance with the work.     

The paramagnetic state (μ+e−) in silicon and tellurium at high temperature

The paramagnetic state (⁺e^–) in Si and Te was observed in a longitudinal magnetic field. The mean lifetimes of these states were obtained: _Si = 1.45(3) s, _Te = 12.5(8) s at 290 K, _Te = 12(2) s at 250 K.     

Efficient multiple-longitudinally diode laser pumped Nd:YAG slab laser

The operation of an eightfold longitudinally diode laser pumped 1.06m cw Nd:YAG slab laser is demonstrated. The 809 nm diode radiation is focused through a dichroic coating into each laser channel starting from the reflection points of the 1.06m beam in the slab crystal. At an absorbed pump power in the crystal of 2830 mW a maximum cw TEM₀₀ output of 1075 mW was achieved with a corresponding slope efficiency of 42.5%.     

Techniques for inelastic X‐ray scattering with μeV‐resolution

A new spectroscopic technique is introduced that allows tuning of a eVwide beam of synchrotron radiation over a range of a few meV. It relies on nuclear resonant scattering that is subject to the Doppler effect in high speed rotary motion. Two mechanisms are discussed how to extract the resonantly scattered radiation out of the broad band of synchrotron radiation: (a) grazing incidence reflection from a rotating disk in combination with a polarization filtering technique and (b) deflection of resonantly scattered radition via the recently discovered Nuclear Lighthouse Effect. Implications for inelastic Xray scattering and elastic nuclear resonant scattering are discussed.     

Quantization of the Maxwell field in linear conformal invariant gauges

It is shown that the generalized Lorentz gauges provide all linear conformal invariant gauges, i.e. gauges such that A =0.     

Surviving extrema for the action on the twisted SU(∞) one point lattice

We give a simplified construction of twist eating configurations, based on a theorem due to Frobenius. These configurations are defined through the equation:U U U ⁺ U ⁺ =exp(2in /N) withU SU(N), =1 tod andn an antisymmetric matrix with integer entries. In the (Twisted)-Eguchi-Kawai model they yield extrema some of which survive forN. Comparison is made with the Monte Carlo data of the internal energy in the small coupling region.     

Experimental investigation of attenuation and backscatter of laser radiation at λ=2.36 μ and λ=0.63 μ by artificial fogs and smokes

The attenuation and backscattering of laser radiation at X = 2.36 and A = 0.63 by artificial fogs and smokes is investigated experimentally. The relationship between the absorption coefficients for these wavelengths is expressed by the linear dependence (2.36) = K (0.63). For fogs with the most probable microphysical parameters K = 1.18, while for smokes, K =0.4. It is shown experimentally that the geometrical parameters of the experimental setup and the optical properties of the scattering medium have a greater effect on the intensity of backscattered radiation than does the wavelength of the incident radiation.Translated from Izvestiya VUZ. Fizika, No. 6, pp. 62–67, June, 1973.     

High repetition rate CH4 laser

A 16-m CF₄ laser oscillator has operated at 1 kHz in a cooled static cell. Pump energies required from the low pressure, Q-switched, cw discharge CO₂ laser were as low as 60 J. The laser cavity employed a multiple-pass off-axis path resonator in a ring configuration. CF₄ laser power at 615 cm^–1 and a 1-kHz repetition rate exceeded 300 W.     

Paramagnetic shift of μ+ in MnO and its time dependence

Conclusion The paramagnetic shift K of ⁺ in MnO is measured from 140K to 420K. K is negative at 14OK, increases rapidly with increasing temperature, but does not show a linear relation to the susceptibility . At T = 170K and 230K, the value of K depends greatly on the fitting time-range of the spectrum. These features are explained by a site change of ⁺ caused by its diffusion and trapping in the crystal.     

Calculations of the Auger deexcitation rate of the dtμ within the muonic quasi-molecule, [(dtμ)dee]

A key process in muon catalysed fusion is the deexcitation of the dt within the resonant muonic quasi-molecule [(dt)dee], by emission of an Auger electron. The dt in the quasi-molecule is initially in a weakly bound excited state withJ=1 andv=1. In this paper, calculations taking full account of the molecular nature of the quasi-molecule are carried out of the rate of the dominant deexcitation to the state withJ=0 andv=1.     

Tunable picosecond infrared pulses generated by stimulated electronic Raman scattering of a mode-locked Ti:Sapphire laser in potassium vapor

A down-conversion to the mid-infrared region by using Stimulated Electronic Raman Scattering (SERS) in potassium vapor is described. The pump radiation is a frequency-doubled regeneratively amplified Ti:Sapphire laser with a pulse duration of 2 ps, pulse energy of 0.2 mJ, and repetition rate of 10 Hz. With the pumping frequency tuned around the potassium 4s-5p transition, nearly transform-limited infrared radiation tunable between 2.2 and 3.4 m has been generated with a peak infrared energy of 12 µJ, corresponding to a quantum efficiency of 17%, and with a pulse duration of 2 ps. The present tuning range could be extended by extending the tuning range of the pump laser. In comparison, intense infrared radiation of 90 µJ energy but with a very narrow tunability around 2.9 m has also been generated by SERS in barium vapor.     

Towards slow μ− production via muon catalyzed fusion

Slow ^– production via dd-CF using a two-layer arrangement is investigated. To determine its feasibility, experimental measurements are now in progress using the muonic X-ray detection method. The following experimental steps are being considered: (1) measurement of the number of ^– stopped inside a solid H₂/D₂ layer by detecting p K X-rays, (2) hot d emission detection by placing a secondary target at a distance of 10–30 mm from the layer and by detecting specific delayed X-rays, (3) measurement of the disappearance of d emission as the added D₂ layer is increased, (4) dd-CF measurement by detecting fusion protons, and (5) slow ^– emission detection. Results of the initial test experiment are presented.     

Optical systems for high-power laser applications: principles and design aspects

Starting from the optical properties of laser beams, the requirements of optical systems for manipulating laser radiation in industrial applications are derived. The relevant parameters, relations to the diffraction limit and the state-of-the-art design techniques are discussed. The three important types of lasers for use in industrial materials processing operate at wavelengths ranging from the infrared (10.6 m, CO₂ laser; 1.06 m, Nd:YAG) to the ultraviolet region (excimer lasers). Each wavelength range is associated with specific design challenges. The scarcity of suitable refractive materials for the 10 m wavelength range and the ultraviolet below 300 nm is a major constraint. Reflective systems are used widely at the longer wavelength, but some designs suffer from coma. The 1.06 m radiation from the Nd:YAG laser can make use of many well-developed optical means for handling visible light. Energy transport by optical fibres is commonly used. Optical systems for excimer laser applications are specific in that they image a mask onto a workpiece, and use the high photon energy and the high definition possible with the short wavelength for precision micro-machining.     

High efficiency cw far infrared lasers at 119 μm and 127 μm

The optically pumped FIR laser lines at 119 m from CH₃OH and at 127 m from¹³CD₃OH are known to be the most powerful in the far infrared spectral region. We report on efficiency measurements for our waveguide laser system. The effect of various parameters was investigated, resulting in the highest efficiency ever reported for the 119 m line. The Stark effect and others parameters of the 127 m were measured, and a new¹³CD₃OH laser line at 175 m discovered, with the same pump transition. These measurements are helpful for completing the assignment already proposed for the 127 m line.     

Efficient vertical-cavity lasers

Recent experimental and theoretical results from strained InGaAs/GaAs quantum-well vertical-cavity surface-emitting lasers indicate that relatively high-power, efficient devices are possible. On 10 m square devices cw output powers of more than 3mW at room temperature and 0.4 mW at 100°C are observed. Broad-area, 100 m diameter devices gave pulsed outputs of over 0.5 W and 60 m diameter devices provided more than 12 mW cw. The device parameters have been modelled and found to be consistent with theoretical predictions. The results generally indicate that considerable device improvements are still possible by reducing internal losses, series resistance and voltage and improving heat sinking. With current internal loss levels 30 cm^–1, three InGaAs quantum-wells have been found to be optimum.     

Reactive pulsed laser deposition and laser induced crystallization of SnO2 transparent conducting thin films

Transparent conducting SnO₂ thin films with a thickness between 1000–2000 Å were deposited on glass, quartz and silicon substrates using standard pulsed laser deposition techniques with two different targets (Sri and SnO₂) and with three different laser wavelengths (1.06, 0.532 and 0.266 ) from a Q-switched Nd: YAG laser. Tin dioxide films with optical transmission over most of the visible spectrum exceeding 80% were obtained using a Sn target and a background oxygen pressure of 20 Pa. The electrical resistivity () depended strongly on the substrate temperature during deposition, with the lowest values of of about 10^–2 -cm obtained when the substrate was maintained at 400°C during deposition. Using SnO₂ targets, predominantly amorphous phase SnO₂ films were deposited on Si substrates and then transformed into polycrystalline Sn₃O₄ by laser induced crystallization ( = 1.06 m). Whereas these later films were essentially non-conducting as deposited ( > 400 -cm), the electrical resistivity was permanently reduced after laser induced crystallization by a factor greater than 1000 to a value of approximately 4 × 10^–1 -cm.