Determination of absorption cross sections for oxygen molecules in the Schumann-Runge band region at high temperatures

We have measured the absorption cross sections of oxygen molecules in oxygen and in an oxygen-argon mixture heated by a shock wave, in the wavelength range 190–250 nm at temperatures of 1500–7000 K, for thermal equilibrium conditions behind the shock wave front. Analysis of the absorption cross sections obtained allowed us to select a data set that adequately describes the absorption characteristics of the electronic transition X³Σ _g ⁻ → B³Σ _u ⁻ for the oxygen molecule. In order to approximate the temperature dependence of these cross sections at a temperature of 1500–4500 K, we chose the function σ(λ, T) = σ₀(λ)(1 − exp (−θ/T)) exp (− n*θ/T) where θ₀ = 1.4·10⁻¹⁷, 1.4·10⁻¹⁷, 1.2·10^{− 17}, and 1.3·10⁻¹⁷ cm², n* = 3.1, 4.1, 5.6, and 7.47 for wavelengths 190, 210, 230, and 250 nm, respectively; θ = 2240 K is the characteristic temperature of the O₂ molecules. The approximation error was 19–25% and did not exceed the experimental error. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 1, pp. 13–17, January–February, 2006.     

Saturation of absorption by lead sulfide nanoparticles in the main absorption band region

The spectral dependence of the degree of bleaching of glasses with PbS nanoparticles (average radius from 3 to 4 nm) has been studied in the main absorption band region. It has been established that the level of residual absorption in the bleached state decreases from 0.70 to 0.02 as we go from the high-frequency edge of the main absorption band for the lead sulfide nanoparticles toward the low-frequency edge, and reflects the spectral features of absorption by charge carriers in excited states. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 2, pp. 195–199, March–April, 2006.     

Theoretical and experimental investigation of millimeter wave phase fluctuations in an absorption region

The differential phase scintillations between two neighbouring frequencies on the side of the oxygen absorption peak have been measured. The –8/3 slope of the asymptotes to the measured spectra at the lowest and highest scintillation frequencies and the spectral ratio between these asymptotes are in good agreement with the theoretical model proposed.     

Quasienergy band structure of solids

The problem of the band structure of solids under the influence of intense laser fields is addressed via the concept of quasienergy bands. The difficulties in evaluation of the quasienergy spectrum in the general case are stated, and a simple effective mass nearly free electron model is treated qualitatively and quantitatively, yielding some useful results.     

Effect of interdiffusion on the band structure and absorption coefficient of a one-dimensional semiconductor superlattice

The effect of interdiffusion of Al and Ga atoms on the confining potential, band structure and absorption coefficient of electromagnetic radiation of a one-dimensional superlattice, composed of GaAs/Ga_1?x Al _x As quantum wells with the initially rectangular potential profile, is studied within the framework of the modified Wood-Saxon potential model. It is shown that the interdiffusion leads to the widening of the energy minibands and to the blueshift of the absorption spectrum observed in experiments.     

Flare angle changes antenna of the millimeter wave band

A pyramidal horn with flare-angle changes was designed at millimeter wave band with using of the S.Cohn's method of antenna pattern shaping. Results of the investigation show an assemblage of good properties are rest-ricted to this kind of antennas (if take into account such parameters as: form of beam, level of sidelobe and crosspolarization, microwave loss and radiation coefficient away from main lobe).     

从吸收比计算光学薄膜的消光系数

对于弱吸收薄腹,当薄膜和基底的折射率在一定数值范围内时,含有吸收比的公式可以用来计算薄膜的消光系数.该式不能用来计算已经没有干涉效应的厚的强吸收膜的消光系数.     

Calculation of absorption coefficient for the ν1 band of sulfur dioxide

The absorption coefficients S/d of sulfur dioxide have been calculated for the ν₁ band for temperatures from 300 ～ 1500°K, taking the major isotopic species S³⁴O₂ into consideration. The total number of the vibrational transitions considered were 4, 10, 23, 41 and 70 for the temperatures of 300, 600, 900, 1200 and 1500°K, respectively. The vibrational energy was calculated to the second order, and the rotational energy and matrix element were calculated exactly with consideration for the asymmetry of the sulfur dioxide molecule. The line intensities greater than 1·0 × 10^-8 cm^-2 atm^-1 STP were included in the calculations. The wavenumber regions of 1000 ～ 1300 cm^-1 were divided into small intervals of Δω = 10 cm^-1 and the S/d averaged over the Δω were obtained. The S/d and some of the line intensities and positions at 300°K were compared with the experimental results of other workers and good agreement was obtained.     

Pulse surface wave generator of millimeter band wavelength

Theoretical and experimental studies of high-power, relativistic surface-wave microwave Cherenkov generators are briefly considered. Some simulation and experiment results included, the experimentation being made in mm-wave region.     

Determination of the absorption constant in the interband region by photocurrent measurements

We determined high absorption constants of crystals from photocurrent measurements within the interband absorption region (10–10⁴ cm^-1). The method has been demonstrated in the interband absorption regime near 530 nm in Sn₂P₂S₆, a novel infrared sensitive photorefractive material, and in the interband absorption regime near 257 nm of near stoichiometric LiTaO₃. Besides the verification of older measurements with our new technique, precise absorption data for Sn₂P₂S₆ in the wavelength range 488–514 nm are presented. PACS 42.70.Nq; 72.41.+w; 78.20.Ci     

Absolute determination of the X‐ray absorption coefficient of barium in the L region using a liquid absorption cell

A method of absolute measurement of X‐ray absorption coefficient is proposed, on the basis of the use of an adjustable pathlength liquid cell and a solution of the investigated element. A variational analysis of the measured data is developed to remove some sources of systematic error. A check of the exponential attenuation with thickness is used to suppress beam harmonics admixture and dark current drifts. The method is illustrated by a measurement on Ba in the L edge region, using aqueous solution of Ba nitrate. Measured data provide information on detailed energy dependence of the absorption beyond the Victoreen‐like trends reproduced in compilations. The proposed method provides a way to measure the absorption data for practically all elements and a wide range of photon energies. Copyright © 2012 John Wiley & Sons, Ltd.