Исследование фотофизических свойств нанокомпозита HgI-=SUB=-2-=/SUB=-@mSiO-=SUB=-2-=/SUB=-

The luminescent properties of a composite consisting of mesoporous silica and mercury diiodide nanoparticles formed in silica nanopores have been investigated. The formation of nanoparticles was carried out by evaporation of a HgI2 solution introduced into the SiO2 nanopores. It was found that photoluminescence of the HgI2@mSiO2 composite was due to emission of mercury diiodide, with the emission spectrum being significantly shifted towards shorter wavelengths with respect to the emission spectrum of bulk HgI2 crystals. The shift of the HgI2 emission spectrum to the short-wavelength side is explained by quantum-size effects in the electronic spectra of HgI2 nanoparticles included in the composite. The significant width of the spectrum is explained by its inhomogeneous broadening due to the dependence of the band gap of the nanodots on their size d. The shape of the size distribution function of HgI2 nanodots was estimated and it was shown that it was characterized by a rather narrow maximum at dM = 2.2 nm, which is 2/3 of the diameter of the nanopores in the SiO2 matrix (~3 nm).

Spectroscopic Properties of TeO2-Bi2O3-ZnO-PbO Based Tellurite Glasses

Tellurite glasses with molar compositions of 55TeO2–2Bi2O3–[43-x] ZnO–xPbO (in mol%) with x= 1, 2, 3, 4, 5 was fabricated by melt quenching method. Their absorption spectra ranging from ultraviolet to infrared region were measured using UV-VIS-NIR spectrophotometer and FTIR. Minimum losses of all glasses were then estimated from the intersection of the ‘V’ curve formed from the intersection of the extrapolation of the IR edge on the long wavelength side of the spectrum and the scattering loss curve on the short wavelength side of the spectrum. From this work, it was that the estimated minimum loss of the investigated glasses were within the range between 2.31·10-3dB/m and 2.94·10-3 dB/m at wavelength around 5.5 μm.

Interaction Potentials of Hg-Ar from Temperature Dependent Absorption Spectra

The temperature dependence of the absorption spectrum k(v̄) of Hg-Ar-mixtures in the range 30-1000 cm-1 about the center of the Hg-line at v̄0 = 39425 cm-1 (λ0 = 2536.5 Å) has been investigated in the temperature interval 473 -1273 K. The measurements were carried out at number densities 1.0 x 1017-9.1 X 1018 cm-3 for Hg and 9.4 x 1018-9.7 x 1018 cm-3 for Ar. Potentials for the Hg-Ar-system in the thermal energy range originating from the Hg-states 61S0 and 63P1 have been deduced from the data. It turned out that they differ considerably from Lennard-Jones-functions. By comparison of the observed spectra with calculations on the basis of quantummechanical theory of collisional line broadening it is concluded that transitions from free translational states of Hg-Ar-pairs as well as bound and quasi-bound vibrational states of the Hg-Ar-molecule contribute to the formation of the satellite structure on the short wavelength side of the Hg-line.

Mass Loss from Stars

The visual spectra of some hot stars, including P Cygni, have emission with associated absorption troughs ˜ 102 km s-1 on the short-wavelength side (Beals 1929, 1951). These P Cygni profiles are easily understood in terms of mass flowing away from the star. Later, rocket observations of the far-ultraviolet resonance lines (Morton 1967) showed that the phenomenon is rather common among hot stars and the velocity shifts could be from 1000 to 3000 km s-1, demonstrating that the mass must be escaping from the star. Resonance lines provide the strongest absorption in the shell where neither the density nor the radiation field is high enough to leave many ions in excited states. Since the ion stages likely to be present around a hot star have their resonance lines shortward of the atmospheric cutoff, space observations are essential in this investigation. Figure 1 shows the P Cygni profile of O VI in ς Pup obtained with Copernicus satellite spectrometer.

A Discussion on astronomy in the ultraviolet - Mass loss from the A-type supergiant α Cygni

The Mg ii resonance lines in a Cygni (A2Ia) are studied from 22 spectral scans obtained by the experiment S59. The cores of the resonance lines are shifted by — 130 km/s and the short wavelength side of the core is shifted by about — 350 km/s. The lines are compared with predicted profiles in an expanding atmosphere. This comparison suggests a rate of mass loss of 3 x 10-10 ^®/year. The atmosphere seems to be accelerated up to a velocity of 300 km/s. The acceleration might be produced by the near-u.v. resonance lines of singly ionized metals. The observations of the near-u.v. spectrum of A-type supergiants with a high spectral resolution is recommended.

Röntgenspektroskopische Untersuchung der chemischen Bindung in Oxiden

This paper reports about the fine structure in the O—K-spectra of the oxides BeO, MgO, CaO, SrO, BaO, Sc2O5, Y2O3, La2O3, Sm2O3, Yb2O3, NiO and ZnO. The spectra show the satellite lines α3, α4, α5, α6 on the short wavelength side of the main line α1,2 and a shoulder β′ on its long wavelength side. The wavelengths of all lines depend on the nature of the oxide. For the positions of the lines Kα1.2 in the spectra no systematic relation to other data of the oxides is observed. On the other hand the distance of the a4-satellite from the α1,2-line decreases with increasing electronegativity of the metal atom in the oxide. This distance can be used as a measure for the ionic character of the metal-oxygen bond in these compounds.

Optical properties of bismuth tri-iodide

The optical absorption spectrum of bismuth tri-iodide has been determined from measurements on single crystals ranging in thickness from 0.35 to 58 µm. At 77 °K the absorption spectrum consists of an absorption doublet A 1 , B 1 (separation 0.38 eV) at 16 900 and 20 000 cm -1 with subsidiary absorption peaks A 2 and B 2 at 18 400 and 21 400 cm -1 . Further absorption bands C and D occur to the short wavelength side of B 2 at ca . 23 500 and 27 600 cm -1 . The absorption coefficients of the peaks have been determined and the oscillator strength of A 1 at room temperature found to be 0.02 per atom (Drude theory). The long wavelength tail of A 1 at room temperature is described by Urbach’s equation. The ordinary reflexion spectrum of single crystals at 77 °K shows reflexion maxima associated with the absorption bands. Measurements have been made of the ordinary refractive index and crystal birefringence. Absorption bands A 1 A 2 and B 1 B 2 are attributed to exciton states associated with (3/2, 1/2) splitting of the valence band. The spectral distribution of photocurrent shows peaks associated with the absorption doublet A 1 B 1 and a sharp increase at short wavelengths due to interband transitions.

The absorption of light by calcium vapour (2100 to 1080 Å)

Continuous absorption and line absorption of radiation in calcium vapour has been measured from the 4 s 4 s 1 S 0 → 4 snp 1 P 1 series limit at 2028 to 1080 Å. Two perturbed series of auto-ionization lines (4 s 4 s 1 S 0 → 3 dnp 1 P 1 and → 3 dnp 3 P 1 ) are recorded and analyzed. A second series limit is observed at 1589 Å. This is probably two unresolved limits corresponding to the two series of auto-ionization lines. No absorption lines are observed on the short wavelength side of 1589 Å. The f -values of the lines vary from 2.4 x 10 -2 to 6 x 10 -5 and the half-lives (calculated from measurements of the half-widths of the lines) vary from 30 to 260 x 10- 15 s. The f -value for the 4 s 4 s 1 S 0 → 4 snp 1 P 1 continuum is estimated to be 0.012 (including an allowance for a portion below 1589 Å) and the f -value for the continua from wavelength 1589 to 1080 Å corresponding to the two series of auto-ionization lines is estimated to be 0.003. The measured value of the absorption near 2028 Å is about one-fiftieth of the theoretical value which has been used in astrophysical calculations.