Short Wavelength Side Research Articles

Photo- and electroluminescence of undoped and rare earth doped ZnO electroluminors

Abstract A series of undoped and rare earth (Dy, Yb, Nd, Pr, Gd, La, Sm and Er) doped ZnO electroluminors have been prepared and their photo-(PL) and electroluminescence (EL) spectra at different concertrations of rare earth ions have been investigated. PL and EL spectra of undoped electroluminors consist of three peaks. Due to the addition of the rare earth ions these peaks are shifted either to the longer or to the shorter wavelength side. The intensities are also either decreased or increased. Experimental results favour the donor—acceptor model for this system.

Das Farbensehen bei Schielamblyopie

Colour vision in squint amblyopia depends on the fixation modus. In eyes with foveolar or unsteady foveolar from fixation the 3 primary colour vision mechanisms (CVMs) gave normal foveolar CVM patterns. The absolute spectral retinal sensitivity was somewhat, but not significantly lowered. The spectral sensitivity for hue discrimination was either normal, or slightly reduced in the short wavelength side, or slightly reduced over the whole visible spectrum. The spectral sensitivity for saturation discrimination showed normal curves. -- In amblyopic eyes with parafoveal to perifoveal fixation mode the absolute spectral retinal sensitivity is lowered for about 0.45--0.60 log units in comparison to an approximately corresponding excentric retinal area in a normal eye. In eyes with parafoveolar to perifoveal fixation mode measurements of CVMs and of hue discrimination gave better results than could be expected with regard to the position of the fixating area as determined by visuscope. The values correspond to those obtained in retinal areas at least as close to the foveola as the amblyopic fixation point, but usually of an even more central position. The sensitivity for saturation discrimination showed no significant disturbance.

Spin orientation effects of shallow electrons induced by magnetization in transition metal surfaces

From infrared reflection measurements of transition metal surfaces it has been found that the profile is sensitively changed by both magnetization and demagnetization. In particular, the longer wavelength side of the reflection edge induced at the 7 – 15 μm region by magnetization with about 300 G is attributed to shallow electrons which are strongly spin oriented. The shorter wavelength side of the edge is due to mixed electrons which are rather weakly spin oriented. The effect of the three types of edge distribution indicates that the interface between the continuum and the mixed level is sensitive to the degree of magnetization; the degree of variation of the magnetic oscillator is estimated from the Nf-R curve to be within the range 10 21 cm -3 - 10 24cm -3.

Interaction Potentials of Hg-Ar from Temperature Dependent Absorption Spectra

Abstract 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.

New satellite structure of the solar and laser plasma spectra in vicinity of the L? (mg xii) line

Spectra in the narrow vicinity of the Mg xii resonance line at λ = 8.42 A were obtained aboard the satellites ‘Intercosmos-4, -7’ and the rocket ‘Vertical-2’, as well as from laser-produced plasma. The high resolution in solar and laboratory spectra made it possible to reveal a new spectral structure close to the Lα (Mg xii) line from both short and long wavelength sides. The main features were observed in all the spectra and were interpreted as a single or group of dielectronic satellite lines due to 2l3l′ → 1s3l″ transitions in the He-like ions according to theoretical calculations which were carried out by means of relativistic Z-expansion technique. The derived electron temperature of the emitting volumes seemed to be ≈ 3 × 106 K for laser plasma and about 6 × 106 K for the solar flares studied. The latter value is in good agreement with the temperature estimated with the help of the resonance line-to-continuum intensity ratios.

Residual absorption in infrared materials

The sources of the residual absorption of ir materials in their transparent region between 2microm and 10microm are reviewed with emphasis upon recent developments. On the longer wavelength side of this spectral region, many insulating crystals are limited by intrinsic multiphonon absorption, and, on the shorter wavelength side, all insulating crystals are limited by extrinsic effects associated with impurities, defects, and surfaces. During the last few years, the general character of the intrinsic multiphonon absorption has become sufficiently well understood so that its frequency and temperature dependence can be accounted for in both ionic and covalent crystals. The nature of extrinsic absorption is more complicated as it arises from a number of sources. In some cases, the measured absorption coefficient can be attributed with some certainty to a specific origin. In others, especially for the ionic crystals at shorter wavelengths, the origin of the extrinsic residual absorption is not known and may be limited by the experimental measurement techniques, at least in some of the better crystals.

Emission from evaporated anthracene films

Emission spectra, excitation spectra and decay times of fluorescence of anthracene films prepared by evaporation on to substrate cooled with liquid nitrogen were measured. The fluorescence spectra of such films show a broad structureless band. The fluorescence excitation spectra and decay times of the emission in the shorter wavelength side of the band are different from those in the longer wavelength side. The decay times of the emissions on the shorter and longer wavelength sides are about 6.0 and 190 ns, respectively, at liquid nitrogen temperature. It may be that the former emission is due to a crystalline structure and the latter emission to an amorphous structure. Next, in anthracene evaporated films containing tetracene as a dopant, the energy transfer from the host to the guest could be observed and this was attributed to the exciton diffusion through the crystalline structure.

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.

Io's sodium emission profiles - Variations due to Io's phase and magnetic latitude

We present recent measurements of high-resolution sodium D2 emission line profiles of Io's atmosphere and cloud. The high-velocity skirts of these profiles are strongest when Io is on the magnetic equator where protons and heavy ions, which sputter atoms from Io's surface, are concentrated. The skirts are most prominent on the long-wavelength side of the line when Io is west of Jupiter, and they are most prominent on the short-wavelength side of the line when Io is east of Jupiter. Our observations also indicate that there is a shift in the emission peak with respect to Io which is correlated with Io's orbital phase angle.

High Dielectronic Satellite Lines in Solar Flare Iron Spectra

New calculations have been carried out in intermediate coupling of the wavelengths and intensities of the Fe XXIV transitions ls2nℓ-ls2pnℓ with n ≥ 3.It is shown that some of these lines are situated on the short wave-length side of the helium-like Fe XXV resonance transition. For the intensities new calculations of the rates of autoionization and radiative decay have been made for the levels involved. Only dielectronic capture has been considered because the contribution of direct inner-shell excitation of the doubly excited states with n ≥ 3 is expected to be small in low density astrophysical plasmas.For this reason both wavelengths and intensities are compared with the only available solar flare Iron spectra of Grineva et al. (1973). Some features not yet identified in these spectra can be explained with the results of the present calculations. These lead to an important new diagnostic capability for solar flare soft X-ray spectra.

The effect of temperature on the visible absorption band of iodine in several solvents

Absorption spectra of iodine in several solvents were obtained at three different temperatures. It was observed that, in all solvents, increasing the temperature led to increased absorption at wavelengths longer than the wavelength of maximum absorption, while the absorption decreased on the shorter wavelength side. The absorption curves at the different temperatures exhibited an isoabsorption point. A plot of the difference in molar absorptivity at two temperatures exhibited, for each solvent, a minimum and maximum in the shorter and longer wavelength regions respectively. A linear relationship was found to exist between the logarithm of the molar extinction coefficient and the reciprocal of the absolute temperature.

Absorption spectra and composition of complexes sorbed in ion exchangers—II: Three-phase distribution analysis in copper(II)-bromide and nickel(II)-thiocyanate complex systems

Visible absorption spectra and compositions of copper(II)-bromide and nickel(II)-thiocyanate complexes sorbed in anion-exchange resin phases have been investigated. The spectral patterns in the resin are considerably different from those in the solution, giving a shift in maximum for both complexes and a new shoulder at the shorter wavelength side of the absorption peak for the nickel-thiocyanate complex. The compositions of the complexes sorbed in the anion-exchange resin from various solutions have been determined by a new method involving three-phase distribution analysis with cation-exchange resin, anion-exchange resin and external solution. The results indicated that the composition varies from a neutral complex CuBr2 to a complex CuBr42− for the copper-bromide complex system and from a cationic complex NiNCS+ to a saturated complex Ni(NCS)64− for the nickel-thiocyanate complex system, respectively, with increase in the ligand concentration.

The wave-shapes and the emission spectra of electroluminescent (ZnS:ZnO):Cu, Sn phosphor

Brightness wave forms of electroluminescent emission in ZnS-ZnO alloy system incorporating copper as activator and tin as co-activator have been investigated at different voltages and frequencies of the applied sinusoidal field. The method of preparation for the new electroluminescent (ZnS : ZnO) Cu, Sn luminophor is described. Voltage and frequency dependence of electroluminescent brightness and spectral distribution have been investigated. The light output varies as B = B0exp(-b/√V) for a wide range of frequencies. The constants b and B0 of this relation have been calculated graphically. The variation of current through the cell follows the relation I ≈ exp (a√V) at low voltages and I ≈ exp(aV) at higher voltages. The peak of the electroluminescent emission spectra shifts towards the shorter wavelength side as the frequency of the applied field is increased.

The interrelationship between cosmic dust and the microwave background

Attention is given to the radiation of microwaves by charged dust in space. Presently-used particle distributions do not restrict the presence in space of large numbers of small (r<10−6 cm) silicate grains, but it is shown that such densities (ϱ≈10−25–10−26 g cm−3) of small grains would produce a microwave background with an energy density of the same order of magnitude as the energy density of the (presumed) cosmological 3 K background. Limits set by the isotropy of the latter are: ϱ(HI clouds)≲10−26, ϱ(Galactic plane)≲10−30, ϱ(Halo)≲10−32, ϱ(Local Group)≲10−34 g cm−3. These limits imply that either there is a cutoff in particle distributions atr≃10−6 cm, or that the density of silicate grains in space has been generally overestimated, or that cosmic rays have broken up a lot of grains so that they now form a population of grains of very small size (≃10−7 cm) which are difficult to detect by conventional methods. One way to look for the latter population is by studying expected distortions of the 3 K spectrum to the short wavelength side of the portion hitherto observed (grains may have a size distribution able to give an approximate black-body curve for radiation from larger grains of 10−6 cm size), and by testing the effective energy density of the 3 K field in other galaxies.

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.

ChemInform Abstract: THE ABSORPTION AND FLUORESCENCE SPECTRA OF 2‐METHYL‐1‐ACEANTHRENONE AND ITS CATION. A COMPARISON WITH 9‐ANTHRACENECARBOXALDEHYDE

The fluorescence and absorption spectra of 2-methyl-1-aceanthrenone (I) and its cation were investigated. The spectra showed well-defined vibrational structures in a wide variety of solvents, but not in ethyl alcohol and acetic acid. The existence of the 1Lb absorption band on the shorter-wavelength side of the 1La band was strongly supported by the different solvent effects of these bands. In non-polar solvents, (I) formed a strongly fluorescent, 1:1, hydrogen-bonded complex with a trichloroacetic acid molecule. The formation constant in n-hexane was determined spectrophotometrically as 3.1×10−2 M−1 at 20 °C. In acidic solutions, pKa and pKa*, were determined as −5.1 and 1.3 for the ground and first excited singlet states respectively. These values are the same as the corresponding values of 9-anthracenecarboxaldehyde (9-CHO-A), reflecting a marked resemblance in the electronic nature of the carbonyl groups of the two compounds. The broad absorption spectra of 9-CHO-A, in contrast to the highly structure...

Photoabsorption of the neutral sodium atom: A many-body calculation

By applying many-body perturbation theory, the effects of electron correlations are included in the calculation for the photoionization cross section of the neutral sodium atom from threshold to 16 eV for the photoejected electron energy. The improvement of the lowest-order Hartree-Fock approximation for the cross section by the first-order and second-order correlation corrections is small. The discrepancy between the experiment and the calculations at the short-wavelength side of the minimum is still not understood.

The Absorption and Fluorescence Spectra of 2-Methyl-1-aceanthrenone and Its Cation. A Comparison with 9-Anthracenecarboxaldehyde

Abstract The fluorescence and absorption spectra of 2-methyl-1-aceanthrenone (I) and its cation were investigated. The spectra showed well-defined vibrational structures in a wide variety of solvents, but not in ethyl alcohol and acetic acid. The existence of the 1Lb absorption band on the shorter-wavelength side of the 1La band was strongly supported by the different solvent effects of these bands. In non-polar solvents, (I) formed a strongly fluorescent, 1:1, hydrogen-bonded complex with a trichloroacetic acid molecule. The formation constant in n-hexane was determined spectrophotometrically as 3.1×10−2 M−1 at 20 °C. In acidic solutions, pKa and pKa*, were determined as −5.1 and 1.3 for the ground and first excited singlet states respectively. These values are the same as the corresponding values of 9-anthracenecarboxaldehyde (9-CHO-A), reflecting a marked resemblance in the electronic nature of the carbonyl groups of the two compounds. The broad absorption spectra of 9-CHO-A, in contrast to the highly structured spectra of (I), are due to a feasible torsional motion of the carbonyl group of the former compound.

Intrinsic fluorescence of a protein devoid of tyrosine and tryptophan: Horse hepatocuprein

The study of intrinsic fluorescence of the protein has recently received much attention. The intrinsic fluorescence is due to the aromatic amino acids phenylalanine, tyrosine and tryptophan. The quantum yield of these amino acids linked in a polypeptide chain is very different. In fact tryptophan is about one order of magnitude more fluorescent than tyrosine, and two orders of magnitude more fluorescent than phenylalanine. Thus proteins containing both tryptophan and tyrosine show almost exclusively the fluorescence of the former, although often it is possible to observe a contribution from tyrosine in the short wavelength side of the spectrum. In the present communication we report the fluorescence spectra of horse hepatocuprein, a cytocuprein with superoxide dismutase activity, which is a metalloprotein devoid of tyrosine and tryptophan. In this protein in the intrinsic fluorescence is solely due to the phenylalanine. This fluorescence is different from that of phenylalanine monomer.

Kβ2 X-ray emission bands of Ga and As and their compounds

Ga and As Kβ 2 emission bands of the compounds under study consist of a more or less pronounced Kβ 2 main band, a short-wavelength side band which according to calculations by the ‘sudden approximation’ method may be essentially assigned to a KM IV,V → M IV,V N II,III satellite, and long-wavelength 3 d → 1 s bands. Compounds such as Ga 2(SO 4) 3, Ga(NO 3) 3, Ga 2O 3, NaH 2AsO 4, K 3AsO 4, and As 2O 3 also show long-wavelength side-maxima at a distance of about 12 and 15 eV, respectively, from the main band, which are due to electron transitions from bands or levels with a preponderant 0 2 s character. The Kβ 2 main band of A III B V compounds is less pronounced owing to the widths of the K levels and to instrumental distortions. The distance between the maxima of the state density of the upper valence bands can be recognized only by a shoulder or asymmetry of the band at the long-wavelength side. By calculation of the Ga and As Kβ 2 bands in GaAs with a pseudopotential kp band structure method, and allowing for the influence of both the transition probability and instrumental distortion excellent agreement with experiment is obtained.