Laboratory Analogues of Cosmic Dust

Mutschke, H.; Clément, D.; Dorschner, J.; Fabian, D.; Jäger, Cornelia; Henning, Th.

doi:10.1017/s1539299600012740

Cited by 42 publications

(91 citation statements)

References 8 publications

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“…Although we could expect the presence of the narrow 11.3 µm emission feature of amorphous SiC grains (optical constants have been taken from Mutschke et al 1999) in stars with C/O ratios close to one, replacing one of the aforementioned dust species with amorphous SiC grains resulted in higher χ 2 values for all spectra. We can confidently state that amorphous silicates, gehlenite and amorphous alumina are necessary to explain the data.…”

Section: Dust Decomposition Toolmentioning

confidence: 99%

TheSpitzerspectroscopic survey of S-type stars

Smolders

Neyskens

Blommaert

et al. 2012

A&A

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Context. S-type AGB stars are thought to be in the transitional phase between M-type and C-type AGB stars. Because the composition of the circumstellar environment reflects the photospheric abundances, one may expect a strong influence of the stellar C/O ratio on the molecular chemistry and the mineralogy of the circumstellar dust. Aims. In this paper, we present a large sample of 87 intrinsic galactic S-type AGB stars, observed at infrared wavelengths with the Spitzer Space Telescope, and supplemented with ground-based optical data. Methods. On the one hand, we derive the stellar parameters from the optical spectroscopy and photometry, using a grid of model atmospheres. On the other, we decompose the infrared spectra to quantify the flux-contributions from the different dust species. Finally, we compare the independently determined stellar parameters and dust properties. Results. For the stars without significant dust emission features, we detect a strict relation between the presence of SiS absorption in the Spitzer spectra and the C/O ratio of the stellar atmosphere. These absorption bands can thus be used as an additional diagnostic for the C/O ratio. For stars with significant dust emission, we define three distinct groups, based on the relative contribution of certain dust species to the infrared flux. We find a strong link between group-membership and C/O ratio. Furthermore, we show that these groups can be explained by assuming that the dust-condensation can be cut short before silicates are produced, while the remaining free atoms and molecules can then be used to form the observed magnesium sulfides or the carriers of the unidentified 13 µm and 20 µm features. Finally, we present the detection of emission features attributed to molecules and dust characteristic to C-type stars, such as molecular SiS, hydrocarbons and magnesium sulfide grains. We show that we often detect magnesium sulfides together with molecular SiS and we propose that it is formed by a reaction of SiS molecules with Mg.

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Section: Dust Decomposition Toolmentioning

confidence: 99%

TheSpitzerspectroscopic survey of S-type stars

Smolders

Neyskens

Blommaert

et al. 2012

A&A

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“…Mutschke et al (1999) have studied the dependence of the spectral appearance of the 11 µm resonance on crystal structure. They concluded that when the crystal is pure, the actual crystal structure is not very important.…”

Section: The Sic Lattice Structurementioning

confidence: 99%

“…First we considered the data as shown before (Laor & Draine 1993). Second we take a rather pure crystal (β-SiC with γ = 10 cm −1 ) according to the equations given by Mutschke et al (1999). Third we consider amorphous SiC as measured by Mutschke et al (1999).…”

Section: The Sic Lattice Structurementioning

confidence: 99%

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The shape and composition of interstellar silicate grains

Min

Waters

Koter

et al. 2006

A&A

191

225

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We investigate the composition and shape distribution of silicate dust grains in the interstellar medium. The effects of the amount of magnesium and iron in the silicate lattice are studied in detail. We fit the spectral shape of the interstellar 10 µm extinction feature as observed towards the galactic center using various particle shapes and dust materials. We use very irregularly shaped coated and non-coated porous Gaussian Random Field particles as well as a statistical approach to model shape effects. For the dust materials we use amorphous and crystalline silicates with various composition as well as silicon carbide (SiC). The results of our analysis of the 10 µm feature are used to compute the shape of the 20 µm silicate feature and to compare this with observations of this feature towards the galactic center. By using realistic particle shapes to fit the interstellar extinction spectrum we are, for the first time, able to derive the magnesium fraction in interstellar silicates. We find that the interstellar silicates are highly magnesium rich (Mg/(Fe + Mg) > 0.9) and that the stoichiometry lies between pyroxene and olivine type silicates (O/Si ≈ 3.5). This composition is not consistent with that of the glassy material found in GEMS in interplanetary dust particles indicating that the amorphous silicates found in the Solar system are, in general, not unprocessed remnants from the interstellar medium. Also, we find that a significant fraction of silicon carbide (∼3%) is present in the interstellar dust grains. We discuss the implications of our results for the formation and evolutionary history of cometary and circumstellar dust. We argue that the fact that crystalline silicates in cometary and circumstellar grains are almost purely magnesium silicates is a natural consequence of our findings that the amorphous silicates from which they were formed were already magnesium rich.

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“…Howa) Electronic mail: alexander.paarmann@fhi-berlin.mpg.de ever, linear optical techniques like reflectivity only provide indirect information, and require differentiation to extract the resonances. 11,12 As one possible solution, nonlinear optical spectroscopy could provide improved sensitivity to critical features in the dielectric response. 13,14 Such studies have been hindered by the sparsity of intense and narrowband laser sources in the mid-IR frequency range and low nonlinear signal levels, such that only few nonlinear optical experiments in the Reststrahl region appear in the literature [15][16][17][18] with no reports for SiC.…”

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confidence: 99%

Second harmonic generation spectroscopy in the Reststrahl band of SiC using an infrared free-electron laser

Paarmann

Razdolski

Melnikov

et al. 2015

Applied Physics Letters

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The Reststrahl spectral region of Silicon Carbide has recently attracted much attention owing to its potential for mid-infrared nanophotonic applications based on surface phonon polaritons (SPhPs). Studies of optical phonon resonances responsible for surface polariton formation, however, have so far been limited to linear optics. In this Letter, we report the first nonlinear optical investigation of the Reststrahl region of SiC, employing an infrared free-electron laser to perform second harmonic generation (SHG) spectroscopy. We observe two distinct resonance features in the SHG spectra, one attributed to resonant enhancement of the nonlinear susceptibility χ (2) and the other due to a resonance in the Fresnel transmission. Our work clearly demonstrates high sensitivity of mid-infrared SHG to phonon-driven phenomena, and opens a route to studying nonlinear effects in nanophotonic structures based on SPhPs.PACS numbers: Second Harmonic, Phonons, Silicon Carbide In recent years, there has been considerable interest in the mid-infrared Reststrahl 1 spectral region of Silicon Carbide (SiC), 2-6 since it holds much promise for a novel approach to low-loss, mid-infrared (IR) nanophotonic applications based on surface phonon polaritons (SPhPs). 4,5 Similarly to surface plasmon polaritons in metals, these surface phonon waves in the Reststrahl band of polar dielectrics can be tailored using resonant optical nano-antennas 4,5 as the fundamental building block of future nanophotonic devices. 7,8 Most importantly, nanophotonics based on SPhPs could solve the intrinsic optical loss-problem of plasmonics, 9 making use of the much smaller damping rates of phonons as compared to plasmons. 6 The peculiar linear optical properties in the Reststrahl region responsible for SPhP formation are dominated by dielectric response of the optical phonons in polar dielectrics. 10 The polar bonding character leads to splitting of the transversal optical (TO) and longitudinal optical (LO) phonon branches at the Brillouin zone-center and IR activity of the zone-center TO phonon. As a result, the TO phonon appears as a sharp resonance in the dielectric function ε(ω) = ε 1 + iε 2 , accompanied with a zero-crossing of ε 1 at the zone-center TO frequency ω T O , whereas the macroscopic polarization associated with LO modes produces the second zero-crossing of ε 1 at ω LO . 10 Therefore, ε 1 is negative between TO and LO phonon frequencies constituting the bulk phonon polariton gap where only SPhPs can exist, defining the Reststrahl band of near-perfect reflectivity. 1,10 In order to improve the engineering of future nanophotonic devices based on SPhPs, exact knowledge of the dielectric response in the Reststrahl region is desired. Howa) Electronic mail: alexander.paarmann@fhi-berlin.mpg.de ever, linear optical techniques like reflectivity only provide indirect information, and require differentiation to extract the resonances. 11,12 As one possible solution, nonlinear optical spectroscopy could provide improved sensitivity to critical featur...

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Laboratory Analogues of Cosmic Dust

Cited by 42 publications

References 8 publications

TheSpitzerspectroscopic survey of S-type stars

TheSpitzerspectroscopic survey of S-type stars

The shape and composition of interstellar silicate grains

Second harmonic generation spectroscopy in the Reststrahl band of SiC using an infrared free-electron laser

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