Short Wavelength Side Research Articles

Velocity-resolved images of molecular hydrogen in the colliding galaxy NGC 6240 - Evidence of a global shock

view Abstract Citations (40) References (21) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Velocity-Resolved Images of Molecular Hydrogen in the Colliding Galaxy NGC 6240: Evidence of a Global Shock Herbst, T. M. ; Graham, J. R. ; Beckwith, S. ; Tsutsui, K. ; Soifer, B. T. ; Matthews, K. Abstract Images of the nuclear region of NGC 6240 taken in the 2.122 micron, ν= 1-0 S(1) quadrupole line of molecular hydrogen demonstrate that the line emission is extended and distinct from the two nuclei producing most of the continuum emission. A region ~ 2" southwest of the southern nucleus produces almost 20% of the total line radiation, yet has no detectable 2 micron continuum. The H_2_ lines are asymmetric, with very little emission on the short-wavelength side of the line peaks. These results indicate that a global phenomenon, such as the dissipative collision of two disks of molecular material, is taking place. The presence of shock-excited material at the same velocity throughout the central kpc of the galaxy and the asymmetry in the S(1) line profile support this conclusion. Global shocks may power the far-infrared luminosity of NGC 6240 as well; if so, the strong H_2_ and infrared emission can persist for no more than ~ 10^6^ yr. Publication: The Astronomical Journal Pub Date: June 1990 DOI: 10.1086/115455 Bibcode: 1990AJ.....99.1773H Keywords: Galactic Nuclei; Hydrogen; Interacting Galaxies; Interstellar Gas; Emission Spectra; Far Infrared Radiation; Resonance Fluorescence; Shock Waves; Starburst Galaxies; Astrophysics; GALAXIES: INTERACTIONS; GALAXIES: INDIVIDUAL full text sources ADS | data products SIMBAD (5) NED (1)

Short continuous radiation on the blue side of Xe I:Xe2 spectrum

Using a transformer discharge through xenon at a pressure of about 200 Torr, a short continuum distinctly different from that already reported for pressure broadened Xe I, has been observed with a reasonably sharp end at 145.2 nm extending towards the short wavelength side up to about 141 nm. The origin of the presently observed short continuum and the four diffuse bands observed by Castex et al. (1974) has been assigned to the transition B'1u-X0g+. The potential curve of C0u+(1S0+1P1) has also been discussed.

Cathodeluminescence from MgO substrates with YBaCuO superconducting epitaxial thin films

Cathodeluminescence (CL) measurements have been performed in MgO substrates with YBaCuO superconducting epitaxial thin films. The luminescence is dominated by the well-known blue emission from the MgO substrate excited through the film. In the CL image, many bright streaks and spots are observed, indicating non-uniform distribution of defects in the MgO substrate. The peak position of the blue emission observed in the anomalous regions is partially or completely shifted to short wavelength side by about 30 nm compared with that of naked MgO substrates. The origin of the peak wavelength shift has been examined and discussed.

Reheating of the universe by unstable neutrinos and cosmic background radiation distortion

view Abstract Citations (17) References (76) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Reheating of the Universe by Unstable Neutrinos and Cosmic Background Radiation Distortion Fukugita, M. ; Kawasaki, M. Abstract The possibility of unstable neutrino reheating of the universe is considered in detail. The evolution equation is integrated numerically with all relevant thermal processes taken into account. We have shown that neutrino reheating can account for the observed distortion of the cosmic background radiation on the short-wavelength side of the peak and that this scenario is consistent with extragalactic background light observations from ultraviolet to infrared regions, if reheating occurs at z ~ 10^4^-10^5^ by heavy neutrinos with a mass 20-10^3^ keV and a photon branching ratio specified by the energetics. Other physical and astrophysical implications are also discussed. Publication: The Astrophysical Journal Pub Date: April 1990 DOI: 10.1086/168624 Bibcode: 1990ApJ...353..384F Keywords: Energetic Particles; Neutrinos; Relic Radiation; Temperature Distribution; Computational Astrophysics; Energy Spectra; Hot Electrons; Universe; Astrophysics; COSMIC BACKGROUND RADIATION; EARLY UNIVERSE; NEUTRINOS full text sources ADS |

Excitation energy transfer from the chlorophyll spectral forms to Photosystem II reaction centres: A fluorescence induction study

Excitation energy transfer from Photosystem II antenna to reaction centres as a function of excitation wavelength, between 646–701 nm, was studied by analysis of the fluorescence quenching efficiency of RCs in both a BBY-grana preparation and thylakoids of the chlorina barley mutant lacking LHCPII. For BBY-grana, maximum transfer was observed with an excitation wavelength slightly greater than 680 nm, with significant decreases occurring for both longer and shorter wavelengths. The data are analysed in terms of the chlorophyll spectral forms as determined by asymmetric gaussian deconvolution of room temperature absorption spectra. For the short-wavelength side of the transfer maximum (646–682 nm) the following relative transfer efficiencies have been determined: 684 > 670 > 650; 678 > 661; 684 > 678 nm. Energy transfer between Photosystem II units is shown to increase with decreasing absorption wavelength below 683 nm. Thus, the above relative transfer efficiencies are associated with transfer to reaction centres within Photosystem II units and not between PS II units. The data are discussed in terms of alternative antenna models. It is argued that they are best accommodated by a model in which the antenna spectral forms have no particular macroscopic distribution with respect to RCs and in which the lower-wavelength-absorbing spectral forms may function as ‘antitraps’ for the longer-wavelength forms as determined by the transfer microparameters. Analysis of the gaussian band associated with Chl b in BBY-grana and LHCII suggest that this antenna component has a low-transition dipole strength within Photosystem II antenna complexes. It is suggested that this will enhance the role of Chl b as an ‘antitrap’ for excited states associated with the longer-wavelength-absorbing chlorophyll species.

Observation of collision-induced-dipole absorption bands in strontium–rare-gas mixtures. I. The 5s–4d bands

Reduced absorption coefficients have been measured for the collision-induced-dipole (CID) absorption bands associated with the 5s–4d transition of atomic strontium perturbed by He, Ne, Ar, Kr, Xe, and Sr. The main CID absorption band, assigned to 5sΣ–4dΣ, extends from the position of the atomic 5s–4d transition towards the shorter-wavelength side for every perturber. For Xe and Kr, an additional small absorption band is seen at the foot of the atomic 5s–4d transition. The former 5sΣ–4dΣ band is interpreted to result from collisional mixing of the 5p state of atomic Sr into the molecular 4dΣ state for small internuclear separations, while the latter band is interpreted to result from the collisional quadrupole (strontium)–dipole (Xe or Kr) interaction.

Effect of composition and growth conditions on the properties of Al xGa 1- xSb epilayers

Al x Ga 1- x Sb ternary compound layers have been grown on GaSb substrates by liquid phase epitaxy using the supercooling technique. Long baking period and large supersaturation temperature ΔT are the critical conditions for the growth of good quality AlGaSb epitaxy. The PL spectra shifted toward the higher-energy (shorter wavelength) side when the Al concentration increased. The composition dependence of bandgap data of Al x Ga 1- x Sb from PL measurement were compared with the numerical results reported by other authors.

Unstable neutrino reheating of the universe and distortion of cosmic background radiation spectrum

It is shown that the unstable neutrino reheating describes correctly the distortion of the cosmic background radiation spectrum in a short-wavelength side of the peak, if reheating occurs between z = 100,000 and 10,000 by the neutrino with mass greater than about 20 keV and the photon branching ratio fixed by the energetics condition. Other astrophysical consequences of reheating are studied in detail. 22 refs.

Infrared multiphoton dissociation of SF6 at long wavelengths

The dissociation probability Pd of 32 SF6 was investigated between 908 and 875 cm−1 at room temperature and at 140 K. In the region of the expected Pd maximum of 36SF6 (≊905 cm−1), we found a ten times higher Pd(32) (implying a ten times smaller selectivity for 36S) than expected from extrapolation of shorter wavelength data. The Pd spectrum in this and in other regions point to an important role of direct multiphoton transitions to levels containing quanta of the neighboring combination mode ν5+ν6 (870 cm−1) besides ν3 quanta. On the short wavelength side of ν3, the analogous transitions involve the ν2+ν6 mode (991 cm−1). The wings, and thus the spectral shape of Pd, in the ν3 region are also governed by them. They depend more strongly on temperature than stepwise transitions, because the intermediate near-resonances favor the high rotational states.

Thallium thin film oxidation investigated by an optical absorption method

Thallium thin films were grown by thermal evaporation onto quartz substrates. The optical absorption spectra of these films were recorded between 220 and 840 nm as the thallium underwent oxidation in the laboratory atmosphere. The spectrum shows an absorption peak which shifts towards the shorter wavelength side as the oxidation increases. This is attributed to a decrease in the metal concentration in favour of oxides. Thin films are almost opaque in the UV region, while in the visible range the transmission increases with oxidizing time. Initially, thallium films follow logarithmic oxidation kinetics in the laboratory atmosphere.

Side-mode injection locking of semiconductor lasers

Longitudinal mode selection in diode lasers by injection locking has been studied using the standard multimode rate equations with an optical injection term, and with the effects of spontaneous emission included. The phenomena of spectral narrowing and power switching between the dominant free-running mode and the injected target mode are illustrated and discussed. In general, injection locking into the long-wavelength side of the spectrum is more effective than into the short-wavelength side because of the gain peak shift. The relaxation oscillation frequency is estimated using a small-signal analysis of the single-mode rate equations, an approach that is valid provided the external injection is strong enough. Our calculations indicate that around the gain peak the relaxation oscillation frequency strongly depends on the wavelength of the injected target mode, because of the changing differential gain. Modes with shorter wavelengths have faster relaxation oscillations due to larger differential gain. This can be helpful in increasing the transmission speed in optical communication applications.

Flat-surface buried heterostructure distributed feedback lasers operating in a single longitudinal mode at 1.5 μm with low chirp

Distributed feedback lasers emitting in a stable dynamic single mode at 1.5 μm wavelength in a temperature range of more than 50 °C have been developed using the so-called flat-surface buried heterostructure. Threshold currents as low as 14 mA in cw (8 mA in pulse) operating and output powers as high as 20 mW/facet were obtained. By detuning the Bragg wavelength to the shorter wavelength side of the gain peak, and by reducing the confinement factor, a wavelength chirp as a function of modulation current as low as 0.003 nm/mA has been obtained. This value corresponds to a total chirp of 0.1–0.2 nm under normal modulation conditions.

Polarized absorption and fluorescence spectra of single crystals of C-phycocyanin

Polarized optical spectra of thin transparent single crystals of C-phycocyanin from Mastigocladus laminosus have been recorded. The isotropic absorption spectra of single crystals differ only at the short-wavelength side of the absorption peak from the corresponding solution spectra. This is presumably due to additional coupling of the β155 chromophores in the crystal. The crystals show dichroism. The position of the absorption maximum shifts between 612 nm ( E parallel to the optical axis c) and 626 nm ( E perpendicular to c) by varying the polarization direction. The observed polarized absorption spectra are compared with theoretical spectra, calculated from the deconvoluted isotropic solution spectra of the individual chromophores (Mimuro, M., Füglistaller, P., Rümbeli, R. and Zuber, H. (1985) Biochim. Biophys. Acta 848, 155–166) and the orientations of the chromophores as determined by X-ray structure analysis (Schirmer, T., Bode, W. and Huber, R. (1987) J. Mol. Biol. in the press). Good agreement is found if the short- and long-wavelength component spectra of the β subunit (β s and β f, respectively) are assigned to chromophores β155 and β84, respectively. The fluorescence polarization spectra indicate that the fluorescence originates predominantly from chromophores α84 and β84, thus giving direct evidence that energy transfer is operative in the crystals and that β84 is the long-wavelength chromophore of the β subunit.

The influence of the water content on absorption and dispersion behaviour of calcium metaphosphate glasses

Calcium metaphosphate glasses were prepared with a water content between 0.005 and 0.16 mol 1 −1 . Properties measured vary in a characteristic way in dependence on the water content. An interpretation for the shift of the absorption edge to shorter wavelength with increasing OH-group concentration, which also explains the change of the glass transition and the recrystallization temperature, is proposed. Dispersion calculations for the wavelength dependence of the refractive index refer to an additional absorption band caused by the OH-groups on the short-wavelength side of the absorption determining the UV-edge

Polarimetry in the Mg ii h and k lines

The Ultraviolet Spectrometer and Polarimeter (UVSP) on the SMM satellite has been used to record the linear polarization profile across the Mgii h and k lines, including its center-to-limb variation. Linear polarization with an orientation of the electric vector parallel to the solar limb is detected in the line wings on the short wavelength side of the k line and on the long wavelength side of the h line, in agreement with theoretical predictions of Auer et al. (1980). The predicted negative polarization (electric vector perpendicular to the limb) between the h and k lines is however not confirmed by the observations. Instead values close to zero are indicated there, although the statistical significance of the results is marginal. We have examined possible explanations of such a discrepancy between theory and observations. After having rejected other alternatives (e.g., opacity effects, different continuum polarization, or deviations from a plane-parallel stratification), it is suggested that the solution may be found in a treatment of partial redistribution of the polarized radiation with the quantum-mechanical interference between the two scattering transitions being included as an integral part of the redistribution problem.

TL and XF spectra in pure and Co-doped NaCl above room temperature

Cobalt impurities in low concentration occupy substitutional sites in NaCl crystal as divalent cations and produce strong charge transfer absorption band at 193 nm. Z centres are not formed in the crystal because of electron trapping nature of the impurity ion. Only two TL glow peaks appear in both pure and Co-doped NaCl, the high temperature glow peak being much stronger than the low temperature one. Interstitials are preferentially stabilised at vacancy pairs and dimers created during irradiation than in existing free or associated cation vacancies. The low temperature glow peak is due to thermal destruction of Cl - 3 ions stabilised at free cation vacancies and the high temperature one to those at vacancy pairs and dimers. The impurity doped crystal has the same emissions as in pure NaCl together with another related to cobalt ion. These emissions arise from the decay of STE formed due to tunneling recombination of electron centres with Cl - 2 ions and the different emissions are due to perturbations of STE by different type of defects. The perturbed STE emission occur on the long wavelength side of π polarised STE emission in NaCl while it occurs on the short wavelength side in KCl. Interstitials have lower mobility in NaCl than in KCl.

Optical Investigations of Rare-Earth Orthochromites. I. TmCrO3

Absorption spectra corresponding to the 4 A 2 g → 2 E g transition of Cr 3+ in TmCrO 3 were studied. In the lowest energy region, R exciton lines with Davydov splitting were observed. Temperature and magnetic field dependences of the R exciton lines suggest that the spin configuration of TmCrO 3 is \(\varGamma_{2}\) above 5 K and the coexistence of \(\varGamma_{2}\) and \(\varGamma_{4}\) below 5 K. In the shorter wave length side of R lines, satellite bands ( R I ′ and R II ′ ) of electric dipole origin were observed. It is shown that the R I,II ′ bands are the combined excitation of a Cr 3+ exciton and the transition from the ground singlet state to the excited singlet states within the Tm 3+ ground multiplet 3 H 6 , and they are induced by the anisotropic parts of the Cr 3+ -Tm 3+ exchange interactions.

Ultraviolet transmission by the ocular media of goldfish: implications for ultraviolet photosensitivity in fishes

Spectral transmittance of goldfish (n = 10) ocular media was measured in the 320- to 750-nm range with a spectrophotometer modified to eliminate problems associated with chromatic aberration and beam scattering. Absolute transmittance in the visible range was 0.8 at 400 nm and 0.95 at 750 nm. Transmittance below 400 nm dropped off to 0.3 at 340 nm and exhibited high variability between individuals. Linear regression analysis showed that ultraviolet (UV) transmittance was not systematically related to age, body weight, standard length, or ocular diameter of fish. Low UV transmittance of the ocular media was shown to influence the UV peak spectral sensitivity by narrowing the action spectrum on the short wavelength side and displacing the UV peak sensitivity to longer wavelengths. Correcting spectral sensitivity curves for ocular media transmittance resulted in agreement with λmax 370 nm absorption spectrum.

Continua in the visible absorption spectrum of K_2

The visible absorption spectrum of the potassium dimer has been studied using a new type of optical cell designed specifically for the alkali vapors or alkali–rare-gas mixtures. Particular emphasis has been placed on examining the diffuse K2 bands lying at 722, 575, 478, and 402 nm. Measurements of the reduced absorption coefficient for each feature are presented, and band assignments are made in light of ab initio potential energy-level calculations for K2 that were recently made by Konowalow and Fish [ D. D. Konowalow , State University of New York, Binghamton, N.Y. (personal communication)]. All the observed features are attributable to extrema in the difference potentials between various pairs of K2 electronic states. In addition, the 575-nm band includes contributions from free → bound (excimer) 1 3Σu+→2 3Πg absorptive transitions of the molecule. Undulatory structure on the short-wavelength side of the 402-nm band has a periodicity of 58 ± 4 cm−1 and is associated with the well-known bound →bound X 1Σg+→D 1Πu transition of K2.

Saturation effects of the 2 eV-photoluminescence in CdMnTe

The rise of the shortwavelength side of the 2 eV-photoluminescence band in CdMnTe during laser excitation shows nonlinear effects which are explained by two-exciton decay processes.