Choosing optical materials for diagnostics of the solar atmosphere in the wavelength range of 6–60 nm

We present our calculations for the reflection characteristics of multilayer mirrors for a series of wavelengths in the interval of 6–60 nm. Interest in these wavelengths is due to preparations for prolonged studies of the Sun within Russia’s ARCA project. For each structure, we suggested a relationship of material layer thicknesses in the period that ensures the optimum reflection coefficient for high spectral selectivity.     

Performance of a polarizer using synthetic mica crystal in the 12–25 nm wavelength range

To develop polarizer functioning in the extreme ultraviolet (EUV) and soft X-ray region, the polarization performance of synthetic mica has been investigated theoretically with a simulation code using Fresnel equations and optical constants from the Henke database. The reflectance of synthetic mica crystal for s and p polarization was measured to investigate its polarization performance in a home-made synchrotron radiation soft X-ray polarimeter at beamline 3W1B, Beijing Synchrotron Radiation Facility (BSRF...     

Absorption Spectra of Gasolines in the Region 1090–1220 nm

The difference absorption spectra of different grades of gasoline (A-76, AI-92, and AI-95) with octane numbers lying within 76–85 have been investigated experimentally in comparison with hydrocarbons: isooctane, benzene, and n-heptane. The spectra obtained contain absorption bands of the CH₃, CH₂, and CH groups and supposedly of the olefin double bond. The possibility of determining the octane number of an unknown grade of gasoline by using the absorption of a measured difference spectrum at one selected wavelength is shown.     

Injection lasers in the 1.3–1.8 μm wavelength range

Conclusion There are developed techniques for the preparation of diode lasers in the 1.3 to 1.8 m range on the basis of quaternary epitaxial heterostructure. Devices for a particular wavelength of 1.3 m are now commercially available. The state of art in the laser studies with connection to lower room-temperature threshold and to higher operation temperature is illustrated in fig. 9. We feel that the laser system of InGaAsP, which is known since 1974 [1, 2], may be elaborated further for higher laser characteristics in spite of the fact that present state is quite acceptable for different applications. There are many fibre-optics projects based on the conception of laser optical communication with the use of diodes in the range of 1.3–1.8 m.Invited talk at the International Conference on Radiative Recombination and Related Phenomena in III–V Compound Semiconductors, Prague, 4–7 October, 1983.The author is indebted to Dr. L. M. Dolginov, B. N. Sverdlov, A. E. Drakin, P. A. Louk, E. G. Shevchenko for the help in this work.     

Attaining the wavelength range 189–197 nm by frequency mixing inβ-BaB2O4

Wavelengths in the range from 188.9 to 197 nm have been obtained by type-I sum frequency generation (SFG) in -BaB₂O₄. The fundamental beams were supplied by pulsed dye lasers one of which tuned between 780 and 950 nm and the other frequency-doubled at 497 nm. The possibility of shifting the excimer wavelength 248.5 nm to the excimer wavelength 193 nm has been demonstrated, replacing the frequency-doubled dye laser by KrF excimer lasers of different beam properties.     

Investigation of the optical constants of arsenic chalcogenide films in the wavelength range 0.5–2.5 μm

Thin films of chalcogenide glasses deposited on quartz glass substrates by thermal evaporation in vacuum have been investigated. The dependences n(λ) and k(λ) for films of different composition have been determined from the transmission spectra. Expressions of the n = A + BL + CL ² + Dλ ² + Eλ ⁴ type (L = (λ ² ? 0.028)^?1 and A, B, C, D, and E are constants) for calculating the refractive indices of As₂Se₃, AsSe₄, AsS₄, and AsS_16.2Se_16.2 films in the wavelength range from 0.5 to 2.5 μm are reported.     

Performance of a polarizer using synthetic mica crystal in the 12——25 nm wavelength range

To develop polarizer functioning in the extreme ultraviolet (EUV) and soft X-ray region, the polarization performance of synthetic mica has been investigated theoretically with a simulation code using Fresnel equations and optical constants from the Henke database. The reflectance of synthetic mica crystal for s and p polarization was measured to investigate its polarization performance in a home-made synchrotron radiation soft X-ray polarimeter at beamline 3W1B, Beijing Synchrotron Radiation Facility (BSRF). The reflectivity of the synthetic mica crystal at an angle of grazing incidence of 48° was obtained from the experimental data, which is about 4.8 × 10^-3 at 25 nm and 6.0 × 10^-4 at 12 nm, and the linear polarizance of the X-ray reflected by the synthetic mica crystal that we measured using an analyzer-rotating method increases from 80% to 96.6% in this EUV region, while higher than 98.2% in the simulation. The result indicates that this synthetic mica crystal works as a practical polarizer in this EUV region of 12--25 nm, and also in an extensive wavelength region higher than 25 nm.     

Measurement of absorption spectra for atmospheric methane by a lidar system with tunable emission wavelength in the range 1.41–4.24 μm

We have developed, built, and tested an automated differential lidar system for measuring low concentrations of atmospheric gases, based on an optical parametric oscillator tunable in the near IR region. We have calculated the spectral shift of the relative intensities of the individual lines in the ν₃ absorption band of methane. In comparing the measured and calculated spectra, we did not observe any shifts in the ν₃ absorption band of methane. At the same time, in the experimental spectra we observe broadening of the Q branch and the individual lines of the P branch. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 2, pp. 285–290, March–April, 2009.     

Characteristics of microwave photoconductivity of natural diamond in the spectral range 200–250 nm

Mechanically polished plates of natural diamond of the IIa and Ia types were investigated by the microwave photoconductivity (MW PC), conventional (direct-current or, more precisely, low-frequency) photoconductivity (LF PC), and optical-absorption techniques. It is shown that the polycrystalline structure of the samples and high spatial inhomogeneity of the impurity defect distribution provide differences in MW PC and LF PC spectra. It is assumed that nonequilibrium holes in the illuminated diamond are trapped by the crystallite boundaries, while free electrons “oscillate” within the crystallites during their lifetime. The influence of chemical and mechanical treatment on the LF and MW PC is demonstrated.     

Investigation of ultrafast processes in photoexcited bismuth by broadband probing in the wavelength range 0.4–0.9 μm

The decay of the photoexcited state of a bismuth single crystal is investigated in the wavelength range from 400 to 900 nm by means of femtosecond laser reflection spectroscopy. Oscillations produced by coherent fully symmetric A _1g phonons have been detected in the photoinduced response, along with a relaxation component. The dynamics of the electronic subsystem of the crystal is shown to be characterized by three values of the decay time: 1 ps, 7 ps, and ∼1 ns. The spectral dependence of the reflectivity oscillation amplitude has been measured; the possible cause of the shape of the derived curve is described.     

Electronic absorption spectra of ascorbic acid in water and water–dialkylsulfoxide mixtures

Gaussian analysis (LinkFit program) was used to deconvolute overlapping absorption bands due to neutral and anionic forms of ascorbic acid (AA). It has been shown that the neutral form of AA predominates in aqueous solutions of AA containing dialkylsulfoxides (DASO) because a hydrogen-bonded complex forms between DASO and AA molecules.     

Narrow-band extreme-ultraviolet laser radiation tunable in the range 90.5–95 nm

Tunable, narrowband extreme ultraviolet radiation in the range 90.5–95 nm with only limited intensity variations is produced by frequency-tripling ultraviolet light from a frequency-doubled dye laser in a gas-jet of xenon. Acetylene gas is found to be an efficient medium for third-harmonic generation in this wavelength range as well. The extreme-ultraviolet radiation is applied in a spectroscopic study of the b ¹ II _u , v=6–8 and v=10–12, o ¹ II _u , v=0 and b¹ _u ⁺ , v=9 states of molecular nitrogen. From linewidth measurements a value k _p=6×10¹⁰ s^–1 for the predissociation rate of the b ¹ II _u , v=11 state is deduced.     

Fluorescence anisotropy of indole molecules under two-photon excitation in the spectral range of 485–510 nm

Decay of polarized fluorescence in indole dissolved in propylene glycol under two-photon excitation by femtosecond laser pulses in the wavelength range of 485–510 nm has been studied. It is shown that under the experimental conditions used the fluorescence decay signal can be well described by a single excited state lifetime τ_f and a single rotation diffusion time τ_rot. By processing the data obtained, the times τ_f and τ_rot as well as anisotropy parameter r ₀ characterizing the symmetry of two-photon excitation of indole molecules have been determined. Decreasing of the anisotropy parameter r₀ down to zero under two-photon excitation energy higher than 5.1 eV has been observed. Interpretation of the obtained results have been done on the basis of ab initio quantum-mechanical computations. A model of energy relaxation under the condition of twophoton excitation of indole in a polar solvent has been discussed.     

Optical properties of human sclera in spectral range 370–2500 nm

Optical characteristics of human sclera are experimentally studied. Experiments are performed in vitro on a Cary-2415 spectrophotometer in the spectral range 370–2500 nm. Based on the measured diffuse reflection and total transmission spectra, the absorption and transport scattering coefficient spectra are calculated by the inverse adding-doubling method.     

New self-developing photopolymers for holographic recording in the 500–700 nm range

The methods of sensitization in the visible spectral region of self-developing photopolymeric materials on the basis of oligoether- and oligourethane acrylates have been investigated. As a result of the choice of the initiating system and modification of the monomer component of the base FPK-488, new FPK-520 and FPK-650 compositions have been obtained that provide holographic recording in the 500–700 nm range. The compositions developed can be used to record holographic optical elements (gratings, lenses) as well as for holographic interferometry and in pattern recognition systems. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 1, pp. 29–33, January–February, 2000.     

Optical spectra of triglycine sulfate crystals in the range of 7–33 eV and its changes at phase transition

Pseudo-dielectric functions ?ε₁(E)? and ?ε₂(E)? of triglycine sulfate (TGS) crystal have been obtained in the range of 7–33 eV for different temperatures close to ferroelectric phase transition by spectral ellipsometry using the synchrotron radiation source BESSY II. These dielectric functions ε₁(E) and ε₂(E) have also been calculated from first principles using CASTEP CAmbridge Serial Total Energy Package code together with the band structure and density of electronic states of the crystal. Experimental and theoretical dielectric functions agree satisfactorily. A characteristic decrease of temperature dependences of the dielectric losses tgδ(T) and related values just below the phase transition temperature T _c have been found and discussed.     

Line-shape study of water vapour by tunable diode laser spectrometer in the 822–832 nm wavelength region

A near-infrared tunable diode laser absorption spectrometer is set up to measure the air-induced broadening coefficients and the line-strength parameters of water-vapour overtone transitions within the (2,1,1)(0,0,0) band in the 822–832 nm wavelength region. A Hitachi HL8311 E double hetero-junction structure diode laser is used as a probe. The diode laser controller is home-built and stable within ±10 A and ±10 mK, respectively. The laser-head mount has a simple design and provides easy access whenever changing of the laser head is required. The diode laser emission wavelength is thermally tuned between 50 °C and 12 °C. Thermal tuning of the diode laser emission wavelength is used to reveal the mode structure of the diode laser and to probe the overtone-band transitions of water vapour within its operating wavelength range. Current tuning of the diode laser is used at a fixed laser temperature to study the transitions one at a time. A balanced detector is used to improve the S/N ratio of the spectrum. A phase sensitive detection technique is followed to obtain the first-derivative spectra of the overtone transitions. The first-derivative spectra have been recorded at different air pressures inside the sample cell while the water-vapour pressure is kept fixed. The first-derivative spectrum is numerically integrated to obtain the original line shape. The original line shape is fitted with a Voigt profile by using a nonlinear least-squares fit program to extract the air-broadening coefficient and the line-strength parameter. The data obtained in our work is compared with the results of the HITRAN database. PACS 33.70.-w; 33.70.Fd; 33.70.Jg     

Optogalvanic spectra of calcium in the 6090–6760 Å region

Optogalvanic spectra of some 30 transitions of calcium originating from the ground state as well as from several excited states (4s4p ^1,3P, 4s3d ^1,3D, 4s5p ³P, 3d4p ³D, ³F) have been investigated using laser-irradiation of a low-current glow discharge in a thermionic diode. The influence of various experimental parameters such as bias field, oven temperature and buffer gas pressure on the spectra are reported. Seven previously unreported transitions are recorded including four forbidden transitions which violate the J selection rules. An interesting anomaly observed in the non-statistical population of the 4s3d ³D_3,2,1 multiplet is discussed where the populations of ³D₃:³D₂:³D₁ are in the ratio of 94:5:1. A possible explanation is based on avoided crossing between potential energy curves of the Ca-Ar molecule.