Optical and electronic properties of heusler Cu<Subscript>2</Subscript>MnAl alloy with shape memory effect

A ferromagnetic Heusler Cu₂MnAl alloy with a shape memory effect has been studied in the wide spectral region of 0.25–2.80 μm (0.44–5.35 eV) at room temperature using spectral ellipsometry methods. Dispersion dependences for optical constants n(hν) and κ(hν), dielectric permeability ε(hν), and optical conductivity σ(hν), which is proportional to the interband density of electronic states, have been analyzed. Optical conductivity spectra have been calculated by mathematical modeling based on data for the electronic state densities in both subbands of electrons with spins oriented along and against the magnetization direction. A model of indirect transitions based on the Berglund–Spicer formula has been shown to describe the experimental spectrum only in general terms. The main contribution to the conductivity in the high-frequency spectral region is due to direct transitions of electrons in the vicinities of L, X, and Γ points of the Brillouin zone coupled with Cu atoms whereas low-energy anomalies in the absorption spectrum σ(hν) are caused by electrons coupled with Mn and Al atoms.     

Optical characteristics of uniaxial polyester films with the optical axis perpendicular to the surface

The functions of the main indices of refraction n(ν) and absorption κ(ν) of uniaxial thin polyethylene terephthalate films have been calculated by the experimental spectra of frustrated total reflection of s-and p-polarized radiation in the 700–760-cm⁻¹ range. The κ_o(ν) maximum falls at the the 727-cm⁻¹ frequency and the maximum of κ_e(ν) falls at the the 724-and 732-cm^{− 1} frequencies. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 6, pp. 756–759, November–December, 2005.     

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.     

High-resolution photoacoustic and direct absorption spectroscopy of main greenhouse gases by use of a pulsed entangled cavity doubly resonant OPO

An entangled cavity doubly resonant optical parametric oscillator (ECOPO) has been developed to provide tunable narrow line width (<100 MHz) pulsed (8 ns) radiation over the 3.8–4.3 μm spectral range at a multi-kilohertz repetition rate with up to 100-W peak power. We demonstrate that coarse single mode tuning is obtained over the full spectral range of oscillation (300 cm⁻¹), while automated mode-hop-free fine tuning is carried out over more than 100 GHz. High-resolution spectra of main greenhouse gases (CO₂, N₂O, SO₂ and CH₄) have been obtained in good agreement with calculated spectra from the HITRAN database. These experiments outline the unique capabilities of the ECOPO for multi-gas sensing based on direct absorption as well as photoacoustic spectroscopy.     

Measurements of the 3ν 3 band of 14N15N16O and 15N14N16O using continuous-wave cavity ring-down spectroscopy

The absorption spectra of the 3ν₃ band of nitrous oxide isotopologues, ¹⁴N¹⁵N¹⁶O and ¹⁵N¹⁴N¹⁶O, have been measured using diode laser cavity ring-down spectroscopy in 6400–6463 and 6465–6532 cm^-1, respectively. Spectroscopic parameters and the rotational line intensities of the bands have been determined. We have applied this spectroscopic technique to the measurements of the absolute isotope ratio of those isotopologues using the absolute line intensities. PACS 32.10.Bi; 33.20.Vq; 33.70.-w; 42.55.Px; 42.62.Fi     

Analysis of glucopyranoside trinitrate IR spectrum

The IR spectrum of 4-O-methyl-2,3,6-tri-O-nitromethyl-β-D-glucopyranoside has been interpreted in detail for the first time based on complete calculation of the normal vibration frequencies and absolute intensities of its IR absorption bands and a comparison of them with the corresponding experimental data. The results indicate that the location of the nitrates in cellulose nitrates can be determined experimentally from separate components of complicated absorption bands in the ranges 1700–1600 and 900–800 cm⁻¹ of the IR spectrum. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 1, pp. 43–51, January–February, 2008.     

Calculations of molecular ir spectra in the overtone and combination frequency regions

Frequencies and intensities of fundamental, overtone, and combination absorption bands have been calculated in an anharmonic approximation for substituted benzene and ethene, aldehydes, ketones, and alcohols in the range 400–4000 cm^–1. The calculated values agree well with the experimental data. It is shown that such a calculation allows one to study and predict dependences of the frequencies and intensities of the overtone and combination bands on the substance structure.     

Low-threshold mid-infrared optical parametric oscillation in periodically poled LiNbO3 synchronously pumped by a Ti:sapphire laser

We report the generation of tunable high-repetition-rate optical pulses in the mid-infrared using synchronously pumped parametric oscillation in periodically poled LiNbO₃ (PPLN). Using a Kerr-lens-mode-locked Ti:sapphire laser as the pump source and a PPLN crystal incorporating grating periods of 21.0–22.4 μm, we have achieved wavelength conversion in the -–4 6μm spectral range in the mid-infrared. The use of a semi-monolithic cavity design and hemispherical focusing has permitted pulse generation in the strong idler absorption region of PPLN, resulting in a simple, compact, all-solid-state configuration with a pump power threshold as low as 17 mW and mid-infrared idler powers of up to 64 mW at 9% extraction efficiency. Signal output powers of up to 280 mW at 35% extraction efficiency are available over the -–1.004 1.140μm spectral range at 80.5 MHz and pulse repetition rates at harmonics of the fundamental frequency up to 322 MHz have also been obtained. Received: 5 December 2000 / Revised version: 23 January 2001 / Published online: 27 April 2001     

μCF Experiments in D2 and HD Gases – Final Results

During 1994–1996, a series of μCF experiments were performed at PSI by the PSI-PNPI-IMEP-LBNL-TUM collaboration. These experiments aimed at high-precision studies of the d–μ–d fusion in D₂ and HD gases in a wide temperature range. The Gatchina ionization time projection chamber has been used to detect the dd-fusion reaction products. The main parameters of the d–μ–d fusion have been measured with high absolute precision. In this report, we present the results of the final analysis of the experimental data. The obtained results are compared with the calculations based on a recent μCF-theory. This revised version was published online in August 2006 with corrections to the Cover Date.     

Theoretical interpretation of spectral signs of an oxymethyl group in the IR spectrum of methyl-β-D-glucopyranoside

For the first time, we have assigned the observed absorption bands and interpreted the IR spectrum of methyl-β-D-glucopyranoside in detail in the 1500–800 cm⁻¹ region, based on a full calculation of the frequencies and absolute intensities of the normal vibrations of the molecule and their comparison with the experimental data. We have identified two groups of spectral signs indicating an oxymethyl substituent has replaced the hydroxyl group on the C₍₁₎ atom in the glucopyranoside: absorption bands of medium intensity due to the characteristic vibrations of the substituent, and intense bands due to an unusual “interaction” between many structural moieties. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 6, pp. 721–727, November–December, 2006.     

Theoretical analysis of the IR spectrum of methyl-3,4-anhydro-α-D-talohexopyranoside

A detailed interpretation of the IR spectrum of methyl-3,4-anhydro-α-D-talohexopyranoside that is based on complete calculation of normal vibration frequencies and absolute IR absorption band intensities of the molecule and a comparison of the results obtained with the corresponding experimental data is given for the first time. The influence of the epoxy group on the absorption bands characteristic of the pyranose ring has been analyzed. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 5, pp. 597–605, September–October, 2008.     

Optical properties and electronic structure of YNi<Subscript>5 − <Emphasis Type="Italic">x</Emphasis></Subscript>Cu<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> intermetallic compounds

The optical properties of hexagonal intermetallic compounds YNi_{5 − x} Cu _x (x = 0, 1, 2) have been investigated by ellipsometry in the spectral range of 0.22–15 μm. It is shown that the replacement of nickel atoms by copper atoms leads to local changes in the optical-conductivity spectra. A new absorption band is found at 3.5–4.5 eV; its intensity depends on the copper content. The plasma and relaxation frequencies of conduction electrons are determined. The electronic structure and interband optical conductivity of these compounds are calculated within the electron density functional theory using the pseudopotential method. The main parameters of the band structure and the total and partial densities of electronic states are determined. Qualitative agreement is obtained between the experimental and theoretical frequency dependences of the optical conductivity.     

Influence of the movement of cylindrical samples with variable internal diameter and variable length along thex-axis of a double TE104 and a single TE102 rectangular cavity on the EPR signal intensity: A sample shape study

The response of the cavity to the movement of cylindrical samples with internal diameters from 0.7 to 4 mm and lengths from 5 to 50 mm along thex-axis of the Bruker double TE₁₀₄ and single TE₁₀₂ rectangular cavity has been analyzed. Independently of sample internal diameter, the experimentally observed dependences of the electron paramagnetic resonance (EPR) signal intensity versus sample position in the cavity showed the following: (i) a sharp maximum for sample lengths from 5 to 20 mm; (ii) a “plateau”, over which the signal intensity remained constant within experimental errors of 0.47–1.16%, for lengths from 30 to 40 mm; and (iii) a “sloping plateau” region, which could be approximated by the linear function (correlationr = 0.96–0.98) for the 50 mm sample. Theoretical predictions of the experimental dependences of the signal intensity versus sample position in the cavity were calculated with the “modified” and “revised” sine-squared function, and the correlation between observed and theoretically computed dependences is very good. Additionally, the experimental dependence of the signal intensity versus the sample internal diameter and length for cylindrical samples situated at the position in the cavity at which the signal intensity was a maximum was likewise numerically approximated by the surface fitting with the Lorentzian cumulative additive function (correlationr = 0.999). The experimental dependence of the signal intensity versus the sample internal diameter for the given sample length is nonlinear. The samples with internal diameters of 0.7 and 1 mm gave the total maximum of signal intensity for the 40 mm sample, however, the samples with internal diameters of 2, 3 and 4 mm gave the total maximal value of signal intensity, which was identical for both the 30 and 40 mm samples. The experimental dependence of the EPR signal intensity versus the sample volume clearly showed that the samples with identical volumes, however, with different shapes, can give significantly different signal intensities (with differences ca. 200–400%). Then, the comparison of cylindrical samples with identical volumes but different shapes may be a serious source of significant errors in quantitative EPR spectroscopy. Cylindrical samples to be compared should be of identical shape. Accurate and precise positioning of each sample in the microwave cavity is essential.     

Formation of compression erosion plasma fluxes of a given composition in dense gases

This article presents the results of experimental investigations of compression erosion plasma fluxes of a given composition determined by the material of the internal electrode; the fluxes have been obtained for the first time in air at atmospheric pressure. It is shown that a compression erosion plasma flux possesses marked absorption in the visible spectral region. The basic thermodynamic parameters of these fluxes were determined with the use of a two-channel system of recording plasma radiation. Reported at the International Conference on Plasma Physics and Plasma Technologies, Minsk, September 15–19, 1997. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 2, pp. 229–233, March–April, 2000.     

Multiphonon absorption in a MgO single crystal in the terahertz range

The reflection and transmission spectra of a MgO single crystal at frequencies of 10–1000 cm⁻¹ in the temperature range 10–300 K have been measured using submillimeter and infrared Fourier spectros-copy. The evolution of anharmonic absorption with variations in temperature has been investigated in the frequency range below the frequency of the transverse optical phonon. The parameters of the dispersion model that adequately describes the lattice absorption of terahertz radiation in single-crystal magnesium oxide have been determined.     

Spectroscopic characteristics of erbiumand ytterbium-activated laser media

Judd–Ofelt parameters (Ω₂ = 5.09∙10^–20, Ω₄ = 0.92∙10^–20, and Ω₆ = 0.63∙10^–20 cm²) and oscillator strengths of fundamental optical transitions involved in lasing at wavelength 1.54 μm have been calculated for borosilicophosphate glass co-activated with Er³⁺ and Tb³⁺ ions based on experimental luminescence and absorption spectra and refractive indices. The results were used to determine the emission (6∙10^–23 cm²) and absorption (5∙10^–21 cm²) cross sections for λ = 1.54 μm and the gain cross section as a function of inverse population levels.     

Optical properties of heated air, carbon dioxide, and argon

Stable-plasma generators, spectroscopic measuring equipment, and methods for determining the optical properties of an extremely heated medium with a given composition have been developed. The spectral coefficients of absorption and emission of heated air, carbon dioxide, and argon were studied. A comparison with the data of other theoretical and experimental investigations has been performed. Deceased. Institute of Molecular and Atomic Physics of the Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 6, pp. 818–826, November–December, 1997.     

Generation of coherent tunable deep UV radiation for detection and absorption studies of explosives RDX and TNT

We report a technique for the efficient generation of tunable coherent deep UV radiation and its application in studies of RDX and TNT at the ppm level on the basis of their absorption characteristics. The obtained experimental absorption data are compared with conventional spectrophotometric data. The UV radiation in the range 200–260 nm has been generated by the type-I noncollinear third harmonic of the dye laser radiation (600–700 nm) and also by sum frequency mixing (SFM) of Nd:YAG output (1064 nm) with the second harmonic of the dye laser in β-barium borate (BBO) crystal. The maximum conversion efficiency of the generated signal is estimated to be 57.5% at λ = 218.9 nm wavelength. Apart from measurements of the absorbance of RDX and TNT at different concentrations in their respective solutions, the minimum detection concentrations have also been ascertained. The estimated minimum detectable concentration of RDX is 8.47·10⁻⁹ M, whereas that for TNT is 35.7·10⁻⁹ M. The data were obtained using only ∼100 μJ/pulse of laser energy. Published in Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 6, pp. 516–521, July–August, 2007.     

Modeling of UV pulsed-laser ablation of metallic targets

A model to describe the laser ablation of metallic targets is presented. It accounts for the main physical processes involved in the laser–solid–plasma interaction by considering the photon absorption and the ionization mechanisms that are active in the plasma, as well as the laser-produced plasma kinetics. The model is used to simulate the laser ablation of aluminum targets irradiated with a 6-ns UV laser pulse at 0.35 μm, and the results are compared with experimental findings. Calculations show that all the investigated plasma parameters strongly depend on the laser intensity until a roll-off is reached at irradiance ≥1.5 GW cm^-2. The satisfactorily good agreement between model predictions and experimental findings confirms that laser–plasma interaction processes and plasma kinetics play a relevant role during nanosecond laser ablation of metals in the laser intensity range of concern in this study. Received: 12 February 1999 / Accepted: 12 April 1999 / Published online: 7 July 1999     

低温辐射计不同结构黑体腔吸收率仿真与实验测量

目前,国际最高光辐射功率基准为低温辐射计,其可探测光谱范围覆盖真空紫外到太赫兹波段(115 nm～T Hz),利用真空低温超导条件下的电替代测量原理,将光辐射功率参数溯源到可以精确测量的电参数进行高精度测量,实现超宽光谱范围的光辐射绝对功率测量,其测量不确定度达到10-5量级,尤其在国防军事和光辐射计量领域,光电有效载...