Sharp Absorption Lines Research Articles

Plaskett's star (HD 47129) - More and more curious

view Abstract Citations (4) References (13) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Plaskett's Star (HD 47129): More and More Curious Underhill, Anne B. Abstract The star HD 47129 appears to be a single-line spectroscopic binary with a mass function equal to 12.6 solar masses. Bagnuolo et al. (1992) have found evidence for the spectra of both stars. They suggest that the spectral type of the primary star is O7.3 I and that of the secondary star is O6.2 I. If so, then two weak sharp emission lines due to C III 5696 A should be seen in the yellow-green spectral region. A spectrogram of HD 47129 was obtained in 1991 November to test this inference. The spectrum was found to be more complex than the description by Bagnuolo et al. suggests. A description of the spectrum from 5300 to 5930 A is presented, and evidence is noted indicating that two rapidly rotating O stars are present. The sharp absorption lines usually attributed to the primary star appear to be formed in plasma which is not surely reflecting the orbital motion of the photosphere of the primary star. The relevant plasma may occupy a disk which is external to the primary star and attached to it. It seems possible that the semiamplitude of the true velocity curve for the primary star is less than the usually adopted value. Such a state of affairs would reduce the mass function for the system. Publication: The Astrophysical Journal Pub Date: June 1993 DOI: 10.1086/172753 Bibcode: 1993ApJ...410..365U Keywords: Binary Stars; O Stars; Stellar Mass; Emission Spectra; Radial Velocity; Stellar Atmospheres; Stellar Rotation; Stellar Spectra; Astrophysics; STARS: INDIVIDUAL HENRY DRAPER NUMBER: HD 47129; STARS: BINARIES: SPECTROSCOPIC full text sources ADS | data products SIMBAD (3)

A Mössbauer study of Fe-Ta-N sputtered films

57Fe Mössbauer measurements have been performed for Fe-Ta-N films deposited by reactive sputtering method. The effect of annealing at various temperatures on the phase decomposition and the magnetic structure of these films has been investigated. For the as-deposited specimen, the 57Fe Mössbauer spectra consist of a paramagnetic component and a magnetically-split component. After annealing at 773 K, the spectra are dominated by a magnetically-split component having a sharp absorption line.

Optical line spectra in metallic (Nd,Ce)2CuO4-x.

Optical absorption lines characteristic of ${\mathrm{Nd}}^{3+}$ have been observed in semiconducting and metallic phases of (Nd,Ce${)}_{2}$${\mathrm{CuO}}_{4\mathrm{\ensuremath{-}}\mathit{x}}$ using a sensitive optical spectroscopic technique. Samples with controlled levels of impurities and controlled cerium content have been studied to verify that the lines observed are intrinsic to (Nd,Ce${)}_{2}$${\mathrm{CuO}}_{4\mathrm{\ensuremath{-}}\mathit{x}}$. Sharp absorption lines in the visible spectrum of these metallic materials are observed. The materials exhibit dichroism characteristic of a two-dimensional conductor. Both this dichroism and the oscillator strengths of certain transitions show variations that are correlated with the doping level, conductivity, and degree of orientation of the samples. It is believed that these variations are the result of changes, induced by the doping, in the charge distribution near the Nd ions and the indices of refraction of the material.

Vibronic spectra of Cu2+ in ZnTe.

Infrared-absorption spectra of substitutional Cu(2+) ions in ZnTe have been measured at 4.6 K. Several distinct absorption peaks are observed between 800 and 2000/cm. Absorption peaks at 1002 and 1069/cm are identified as zero-phonon lines arising from 2T2-2E transitions. Between 1069 and 2000/cm, several sets of sharp absorption lines are seen to recur regularly at an interval of 210/cm, corresponding to the LO phonon energy. Within each set distinct vibronic sidebands that cannot be identified with critical-point energies of TA, LA, TO or LO phonon modes are observed. A dynamic Jahn-Teller effect, involving coupling between a single-phonon mode and the electronic states of the 2E level, is proposed to account for the observed spectra.

Polarized optical absorption spectra of synthetic chromium doped Mg2SiO4 (forsterite)

Polarized optical absorption measurements were carried out on three single crystals of Mg2SiO4 (forsterite), differently doped with Cr. Two crystals containing average 0.013 and 0.027 weight% Cr, respectively, were pulled from the melt in air, whereas one crystal containing average 0.08 weight% Cr was pulled from the melt in an argon atmosphere. The absorption spectra of the three crystals agree with each other although the intensity of single absorption bands varies significantly. In all γ-polarized patterns a sharp absorption line around 18000cm-1 (550 nm) appears. Conjectures are presented to assign this line to the lasing center in Cr doped forsterite which very likely exists as Cr4+ at the fourfold coordinated Si site.

Detection of sharp absorption lines in thin NdF_3 films

We report the use of a sensitive spectrometer system for studying sharp optical absorption lines that are due to transitions between 4f3 crystal-field levels of Nd3+ in epitaxial NdF3 films. Films as thin as 50 Å on GaAs substrates displayed absorption lines with asymmetric line shapes. Samples with an antireflecting LaF3 buffer between the NdF3 layer and the substrate permitted observation of absorption lines in thinner films.

Van der Waals epitaxial growth of thin BiI3 films on PbI2 and CdI2 substrates by a hot wall method

A hot wall technique was applied to grow very thin BiI3 single crystals about 100–1000 Å thick by the achievement of low-temperature growth. The so-called van der Waals epitaxy became possible by employing layered materials such as PbI2 and CdI2 as substrate. BiI3 thin films grown with optimized conditions exhibited a sharp band-edge direct exciton absorption line of 30-meV half-width, which is much sharper than that of a single crystal grown by a conventional method reported so far. The transmission electron diffraction measurements were carried out on the films. It was revealed that highly perfect single crystals with a 4-mm diameter size were obtained.

Complex microwave susceptibility of natural squid structures

Dispersive behavior associated with the sharp periodic absorption lines that have been attributed to fluxon nucleation within Josephson junctions has been observed in single crystals of YBa2Cu3O7−δ. Both the absorption and dispersion signals are interpreted with an rf SQUID model that associates the absorption signal with hysteresis and the dispersive signal with constant flux. The observed broadening above a threshold in microwave power of the absorption and dispersion into bands is given a particularly simple interpretation with the rf SQUID model. The observed constancy of the absorption amplitude with increasing rf power may also be interpreted simply on the basis of hysteresis.

Large Optical Nonlinearity of the Two‐Dimensional Exciton States at a Stacking Fault Interface in BiI3

AbstractThe optical Stark effect of an exciton system localized at a stacking fault (stacking fault excitons, SFE) in BiI3 crystals is presented. The SFE states show three very sharp absorption lines called R, S, and T. The excitation laser frequency dependence of the peak shift of the absorption line T is observed in a wide frequency range covering the three SFE states. The peak shift can be seen even for far off‐resonance excitation, and shows drastic change for the on‐resonance excitation of R, S, and T states. This behaviour can be explained by a “dressed exciton” model. The excitation intensity dependence of the peak shift manifests a very large nonlinear optical polarizability of the SFE system.

Excitons in layered BiI 3 single crystals

This paper reviews the various exciton spectra in the absorption edge of BiI 3 crystals, which show many aspects of exciton behavior. The band edge exciton transition takes place with a very large oscillator strength and is ascribed to rather localized s→p transition in Bi 3+ ions. Its anisotropy and surface effects are characterized by a van der Waals bonded layered lattice. A series of very sharp absorption lines near the edge is attributed to direct exciton transitions in a stacking fault plane, and the resonant emission lines can be observed with no Stokes' shift. Their conspicuous properties, including the relaxation process, high excitation effects, propagation along the plane and so on, are summarized and discussed in terms of an exciton system confined in a nearly perfect two-dimensional lattice. The necessity and desirability of more complete studies of the stacking fault exciton system are emphasized.

Discovery of a quadruply lensed quasar: the 'clover leaf H1413 + 117

In November 1986 we began an optical search for examples of gravitational lensing in a sample of highly luminous quasars (HLQs, Mv < –29), with the aims of improving our knowledge of the quasar luminosity function, studying the dark matter content of the Universe, and redetermining some important cosmological parameters. This survey has found one new case of lensing1,2 and the general implications of the search have been summarized3. Here we report the discovery of a second gravitational lens system in the broad absorption line quasar H1413 + 117 (refs 4–6). Four images of comparable brightness are seen, separated by ˜1 arcsec. Spectra obtained of two of the images are identical apart from the presence of sharp absorption lines in one component, which are presumably due to gas clouds along the line of sight. The unique configuration of the images, together with the fairly rare occurrence of this type of quasar, makes it incontrovertible that this is a lensed system, not a cluster of quasars, and this second discovery made by imaging bright quasars establishes the power of the method for finding systems with small separations.

Optical properties of excitons confined two-dimensionally in a stacking fault plane in BiI 3

Extremely sharp absorption and luminescence lines due to the transitions of stacking fault excitons in BiI 3 show characteristics polarization properties. These behaviours are discussed on cationic exciton model in the deformed lattice at the stacking fault.

Nonlinear excitonic optical absorption in GaSb

We have measured the saturation of optical absorption in GaSb at wavelengths close to the band gap, and have determined the nonlinear absorption (α2) and refraction (n2) coefficients. At liquid-helium temperature a sharp free-exciton absorption line is observed which saturates with increasing incident laser intensity; we obtain values ‖α2‖=70 cm W−1 and ‖n2‖≊0.2 cm2 kW−1. At room temperature we do not observe a well-defined exciton; saturation of the residual interband absorption occurs at much higher intensity, and it is found to be obscured by strong thermal effects.

Very thin PbI2 single crystals grown by a hot wall technique

A hot wall technique was applied to grow PbI2 thin films of about 100 nm thickness on cleaved surfaces of CdI2 single crystals. The band-edge exciton absorption spectra were investigated for the films grown in various conditions. A very sharp exciton absorption line of 8.8 meV half-width was obtained in a PbI2 single-crystal film grown at a 75 °C substrate temperature. The sharpness of the exciton line proved the excellent quality of the PbI2 film and the usefulness of the technique.

Evidence for hydrogen-transition-metal complexes in as-grown indium phosphide

Indium phosphide single crystals doped with transition metal impurities display sharp optical absorption lines around 2300 cm -1. Each line seems to be characteristic of a specific transition metal impurity. The behaviour of these lines as a function of temperature suggests that they are of vibrational nature rather than of electronic one. These lines are attributed to the vibrational mode of a P-H bond; the hydrogen is a nearest neighbour to the transition metal impurity. In this way, the “chemical shift” of the line is characteristic of the transition metal impurity.

Evidence for Complexes of Hydrogen with Impurities or Defects in Bulk III-V Materials

ABSTRACTSeries of sharp optical absorption lines around 2200 cm-1 in GaP, 2000 cm-1 in GaAs, and 2300 cm-1 in InP are observed in bulk materials. They are shown to be due to stretching local modes of vibration of P-H or As-H bonds, the hydrogen sitting nearby an impurity or defect. The origin of the hydrogen contamination of the bulk materials is discussed.

Satellite Phonon Absorption Lines above the 875 GHz Resonance of Interstitial Oxygen in Silicon

Acoustic phonon spectroscopy with superconducting tunneling junctions as phonon generator and detector revealed a large number of sharp absorption lines between 875 GHz (oxygen resonance) and 1.35 THz for silicon doped with interstitial oxygen (Si:0i). The strength of these lines scales with the square of the oxygen concentration ranging from 1017 to 1018 cm-3. Under mechanical stress the lines show a frequency shift almost identical to the main oxygen resonance at 875 GHz as well as to the also observable isotope resonance. These satellite absorption lines are therefore discussed as 0i–0i neighbour interaction. This is supported by the influence of annealing.

Optically induced changes of the Cr-related absorption lines in GaP:Cr-evidence for internal transitions of CrtGa3+

The authors have investigated the optically induced decrease of the CrGa2+ (5T2 to 5E) absorption line structure at 0.87 eV in GaP:Cr and the accompanying increases of the 1.03 eV sharp-line absorption structure and of the broad 1.32 eV absorption band. The measurements are consistent with the assignment of the latter two features to internal transitions of CrGa3+.

Compression of phase-switched optical pulses in a resonant absorber

The problem of pulse compression in a medium presenting a sharp absorption line is examined with emphasis on the resulting enhancement in the peak power. The largest enhancements are shown to be achieved by switching the phase of the input pulses according to a well-defined sequence. The effects due to the rise time of the phase-switch are discussed and enhancements ≈ 160 in the peak power of optical pulses are predicted to be attainable in an atomic vapor with a realistic switching time (50 ps).

Optical Properties of Extrinsic Two-Dimensional Excitons in BiI3Single Crystals

Interface excitons caused by stacking faults in BiI 3 , crystals have been investigated on absorption, photoluminescence and its excitation spectra. Characteristic three sharp absorption lines (called R , S and T ), appear close to the fundamental absorption edge. The temperature dependence of the line shape shows a typical feature of exciton-phonon interaction in the case that K =0 at the bottom of the exciton band. Resonant luminescences of these lines have also very narrow line widths, and no Stokes shifts can be detected. The luminescence line shape of phonon side band shows Maxwellian-like having the line width proportional to thermal energy but accompanied by a fine structure which reflects a quasi two-dimensional band nature of this exciton system. The high density excitation effects of these states reveal a specific interaction among the R , S and T excitons.