A superpowerful source of far-ultraviolet monochromatic radiation

In several independent experiments investigating the interaction between the optical field of an intense laser pulse and a xenon cluster beam, we recorded an anomalously high quantum yield of the plasma radiation in the region 10–15 nm. In several cases, the conversion efficiency into the hemisphere reached 10% of the pumping pulse energy. The nature of this phenomenon has not yet been adequately explained. A high conversion efficiency is shown to be possible when producing a plasma with optimal parameters for the amplification of spontaneous radiation on Ni-like xenon transitions to be generated. In a collisional-radiative model, we performed detailed atomic-kinetic calculations of the gains and radiation spectra on the transitions with λ ≈ 4, 10, and 11.3 nm and in the region 13–13.9 nm. For each transition, we determined the time dependences of the gains on plasma parameters. The theoretical and experimental values of the optimal plasma parameters and energy yields of the radiation are in close agreement. Using a theoretical model, we propose possible plasma pumping schemes to achieve the maximum yield of the intense, narrowly beamed soft X-ray radiation. At a pumping pulse repetition rate of 10⁴ Hz, the output power for various Ni-like xenon transitions ranges from 100 to 5 × 10³ W.     

Study of the frequency distribution of the fluorescent light induced by monochromatic radiation

The frequency distribution of the fluorescent light induced by monochromatic dye laser radiation was investigated. To exclude the influence of the Doppler width a strongly collimated atomic beam was used. The spectrum was measured by means of a piezoelectrically tunable spherical Fabry Perot. The interaction region between the laser light and the atomic beam was placed into the center of the interferometer. Thus the observed fluorescence spectrum was considerably more intense than in the case where the interferometer is used separately from the beam. The fluorescence spectrum was observed for different directions of polarization of the incident laser beam. In the case of weak excitation the spectrum consists of a sharp component essentially due to elastically scattered light. At high intensities a structure of three components is observed which is in agreement with theoretical predictions when circularly polarized light is used for excitation.     

Study of the frequency distribution of the fluorescent light induced by monochromatic radiation

The frequency distribution of the fluorescent light induced by monochromatic dye laser radiation was investigated. To exclude the influence of the Doppler width a strongly collimated atomic beam was used. The spectrum was measured by means of a piezoelectrically tunable spherical Fabry Perot. The interaction region between the laser light and the atomic beam was placed into the center of the interferometer. Thus the observed fluorescence spectrum was considerably more intense than in the case where the interferometer is used separately from the beam. The fluorescence spectrum was observed for different directions of polarization of the incident laser beam. In the case of weak excitation the spectrum consists of a sharp component essentially due to elastically scattered light. At high intensities a structure of three components is observed which is in agreement with theoretical predictions when circularly polarized light is used for excitation.     

Formation of the contour of a spectral line upon partial frequency redistribution

The problem of the radiation transfer in an atomic gas in a laser radiation field is numerically solved under the conditions of partial frequency redistribution and cylindrical geometry of the medium. The light scattering by atoms is modeled by the angle-averaged distribution function R _III. The influence of the partial frequency redistribution on the formation of the sodium emission line λ = 589.6 nm and on the characteristic deexcitation time of the sodium vapor is studied in relation to the vapor optical thickness.     

Collisional redistribution of radiation

The subject of this review is the collisional redistribution of resonance atomic radiation in dilute gases. The formation of scattered spectra in weak and intense fields is discussed and the formation that may be obtained from experiments is presented. The focus of recent work in the field is on radiative events taking place during collisions. Different aspects of the problem are presented using mainly the density matrix and correlation function approach. This work has shown what types of information on interatomic potentials and collision dynamics can be obtained using near-resonant light scattering from gases: this is highlighted in a discussion of light scattering in the presence of depolarizing collisions. We discuss the relationship of work on collisional redistribution to the various “half-collision” experiments that have recently come to the fore.     

Influence of the periodic motion of a monochromatic light source on the spectrum of its radiation

The influence of the periodic motion of a monochromatic light source on the observed spectrum of its radiation in the far-field and near-field zones is considered. The appearance of components shifted in frequency (harmonics of the oscillation frequency of the source) is demonstrated. The spatial structure of harmonics is investigated, and the presence of optical vortices in these harmonics is shown.     

部分相干源实验研究

 在无阶梯诱导空间非相干光束平滑技术中，用作前端的部分相干源是重要的组成部分。介绍了利用准分子激光进行的部分相干源实验，发现聚四氟乙烯是一种较理想的散射材料。研究了聚四氟乙烯散射源对光束的散射性能，给出了光束均匀性、空间相干性和能量转换效率等参数。     

Passage of monochromatic radiation through a resonance radiation absorbing medium

The problem of passage of monochromatic radiation pulses through a one-dimensional medium containing several types of nonuniformly distributed absorption centers with coincident energy levels are considered. The physical picture associated with the effect of a brightening wave arising in an optically dense absorbing medium is analyzed. The investigated relations represent a generalization of Bouguer's law for the case of powerful fluxes of monochromatic radiation with allowance for absorption saturation.     

Nonlinear absorption of monochromatic radiation in gases

The absorption coefficient as a function of the density of monochromatic collimated radiation is discussed for an arbitrary ratio of natural to Doppler width, with allowance for the effects of collisions between molecules.We are indebted to M.A. El'yashevich for a discussion and to Ya. S. Vasilevskaya and UP. Pesotskaya in preparing the paper.     

Radiative transfer with partial frequency redistribution in inhomogeneous atmospheres: Application to the Jovian aurora

A direct finite difference numerical solution for the equation of radiative transfer by the Feautrier method is developed for use in planetary atmospheres. The procedure described here uses a plane-parallel atmosphere, and can treat partial frequency redistribution, inhomogeneity, external or internal sources, and various boundary conditions. Isotropic scattering is assumed, but in the case of no frequency redistribution, Rayleigh scattering can also be handled. A program utilizing this method is tested in a variety of situations against more powerful and elaborate methods. The case of the Lyman-α aurora on Jupiter is then considered, where the effects of partial frequency redistribution are shown to be of great importance. New results for the detailed line profiles for Lyman-α in the Jovian aurora are presented. The method is quite versatile, and should be especially useful in studying a wide range of problems related to auroral or dayglow emissions in planetary atmospheres.     

A hydrodynamic X-ray radiation source

The results of experimental investigation of a flow of a weakly conductive liquid in a coaxial channel with insulating walls are presented. The possibility of forming all the necessary conditions to generate X-ray radiation when liquid moves in the channel is shown. The questions of the electrization, the charge accumulation, and its discharge are considered. It is shown that the charge intensely accumulates during liquid cavitation in small holes on the channel wall. The appearance of stable luminous cavitation threads moving in the flow is revealed in the initial segment of the channel, and their role in the discharge of the cavitation regions is determined.     

Testing of a cryogenic source of slow monochromatic positrons

The results of testing a cryogenic source of slow monochromatic positrons based on the ²²Na isotope, designed and constructed at JINR, are presented. A solid neon moderator was used to generate a monochromatic beam from the continuous β⁺ spectrum of 0–0.5 MeV, with solid neon being frozen to the base layer, which is cooled to the temperature of 5–7 K. Test source of the ²²Na isotope allows the forming of a slow positron beam of intensity 5.8 × 10³ part./s and the average energy 1.2 eV at a spectrum width of 1 eV. The efficiency of moderation is 1% of the total positron flux.     

Observation of subterahertz monochromatic transition radiation from a grating

Transition radiation appearing when a charged particle crosses the interface between two media with different dielectric constants, e.g., a metal–vacuum interface, has been well studied in a wide spectral range. However, primarily, radiation from smooth interfaces has been studied. Transition radiation from conducting gratings (grating transition radiation) is experimentally studied and theoretically analyzed in this work. In this case, it is possible to obtain monochromatic radiation with a tunable frequency depending on the rotation angle of the grating with respect to the electron momentum. Coherent grating transition radiation can be efficiently used as a source of terahertz radiation based on the use of a compact electron accelerator with an energy below 10 MeV and a bunch duration of ≤1 ps.     

A monochromatic and frequency stabilized cw source in the 5 μm region obtained by doubling the frequencies of a cw laser in tellurium

In this paper we describe the construction of a monochromatic and frequency stabilized continuous wave (cw) source in the 5 μm region. It is built up by a cw single line, single-mode frequency and amplitude stabilized CO₂ laser. This primary CO₂ laser source is then frequency-doubled in a tellurium crystal using second harmonic generation (SHG). The obtained emission is monochromatic (half-width 50 kHz). The frequency can be varied discreetly from 4.6 μm to 5.5 μ depending on the CO₂ laser line chosen.     

高功率超宽谱辐射源实验研究

对高功率超宽谱辐射源的参数进行了理论分析设计,对高压电源、脉冲产生、阻抗变换及传输线、天线等各部分的具体参数进行了分解匹配。根据理论计算结果,设计了一套高功率超宽谱辐射装置并进行了实验研究,对输出功率、辐射效率等进行了调试,在2.7 Ω负载上获得脉冲输出功率超过30 GW、脉冲宽度1.6 ns,通过超宽谱Cassegrain双反射面天线辐射,等效辐射峰值功率超过2×1012 W,辐射因子超过8 MV,H面与E面3 dB宽度分别为2.35°和2.27°。     

基于荧光显微镜单色光源系统的椭球反射镜的设计

为了实现胞内钙离子浓度的检测，设计了一种新型的荧光显微镜单色光源系统。系统采用短弧氙灯作为发光源，利用椭球面反射镜聚焦后得到模拟的点光源，经过准直及闪耀光栅分光、汇聚后，耦合到光纤中形成单色光输出。在荧光显微镜照明激发系统中，单色光源的输出功率和光谱纯度是仪器的2个技术关键，其中非球面反射镜是设计的重点。通过优化算法和光学仿真模拟，对系统的光能效率进行了分析和计算，设计了用于单色光源系统的椭球面反射镜，并研制成整套系统。经实验验证，效果良好。     

Applicability of the probability model to absorption of monochromatic radiation

A kinetic equation is derived for the forced population relaxation in a gas in the limiting case of sharp collisions (with complete loss of phase coherence). The solution is examined for the conditions under which it satisfies the basic kinetic equation of the transition model.