Quenched carbonaceous composite. III - Comparison to the 3.29 micron interstellar emission feature

Sakata, Akira; Wada, Setsuko; Onaka, Takashi; Tokunaga, A. T.

doi:10.1086/168642

Cited by 42 publications

(34 citation statements)

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“…1. They show several absorption features similar to the UIR bands observed in celestial objects (Sakata et al 1984(Sakata et al , 1987(Sakata et al , 1990. For the filmy-QCC with 1% 13 C the bands of the C−H stretching characteristic group appear at 3.29, 3.42, 3.51, and 3.53 µm (see also Fig.…”

Section: Spectra Of Filmy-qccsupporting

confidence: 59%

$\mathsf{^{13}}$C isotope effects on infrared bands of quenched carbonaceous composite (QCC)

Wada

Onaka

Yamamura

et al. 2003

A&A

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Abstract. We investigate carbon isotope effects on the infrared bands of a laboratory analogue of carbonaceous dust, the quenched carbonaceous composite (QCC), synthesized from a plasma gas of methane with various 12 C/ 13 C ratios. Peak shifts to longer wavelengths due to the substitution of 12 C by 13 C are clearly observed in several absorption bands. The shifts are almost linearly proportional to the 13 C fraction. New features associated with 13 C are not seen, indicating that the infrared bands in the QCC are not very localized vibration modes but come from vibrations associated with rather large carbon structures. An appreciable peak shift (∆λ ∼ 0.23−0.26 µm per 13 C fraction) is detected in the 6.2 µm band, which is attributed to a carboncarbon vibration. A peak shift (∆λ ∼ 0.16−0.18 µm per 13 C fraction) in an out-of-plane bending mode of aromatic C−H at 11.4 µm is also observed, while only a small shift (∆λ < 0.015 µm per 13 C fraction) is detected in the 3.3 µm band, which arises from a C−H stretching mode. The present experiment suggests that peak shifts in the unidentified infrared (UIR) bands, particularly in the 6.2 µm band, should be detectable in celestial objects with low 12 C/ 13 C ratios (<10). The isotopic shifts seen in the QCC are discussed in relation to the variations in the UIR band peaks observed in post-asymptotic giant branch stars and planetary nebulae. The observed peak shift pattern of the UIR bands is qualitatively in agreement with the isotopic shifts in the QCC except for the 7.7 µm band complex although the observed shifts in the UIR bands are larger than those inferred from derived isotope ratios for individual objects. The poor quantitative agreement may be attributed partly to large uncertainties in the derived 12 C/ 13 C, to possible spatial variations of the isotope abundance within the object, and to combinations of other effects, such as hetero-atom substitutions. The present investigation suggests that part of the observed variations in the UIR band peaks may come from the isotopic effects.

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Section: Spectra Of Filmy-qccsupporting

confidence: 59%

$\mathsf{^{13}}$C isotope effects on infrared bands of quenched carbonaceous composite (QCC)

Wada

Onaka

Yamamura

et al. 2003

A&A

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“…The possible carriers presented so far are all successful in reproducing the spectral shape from 3.3 to 3.4 lm. These include a mixture of PAH molecules fully reprocessed by energetic hydrogen plasma (Beegle, Wdowiak, & Arnoult 1997;Arnoult, Wdowiak, & Beegle 2000), carbon nanoparticles produced by laser pyrolysis of C 2 H 4 and C 4 H 6 (Herlin et al 1998) or C 2 H 2 (Schnaiter et al 1999), hydrogenated amorphous carbon prepared by eximer laser ablation of graphite in a hydrogen rich atmosphere (Scott, Duley, & Jahani 1997;Grishko & Duley 2000), and quenched carbonaceous composite produced by the plasma deposition technique with CH 4 (Sakata et al 1990;Goto et al 2000). Semianthracite coal grains (Guillois et al 1996) are also successful in reproducing the aliphatic band at 3.4 lm and substructures in the mid-infrared feature and overall continuum shape.…”

Section: Hydrocarbon Dust Emission At 33-34 Lmmentioning

confidence: 99%

Spatially Resolved 3 Micron Spectroscopy of IRAS 22272+5435: Formation and Evolution of Aliphatic Hydrocarbon Dust in Proto–Planetary Nebulae

Goto

Gäessler

Hayano

et al. 2003

ApJ

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We present medium-resolution 3 lm spectroscopy of the carbon-rich proto-planetary nebula IRAS 22272+5435. Spectroscopy with the Subaru Telescope adaptive optics system revealed a spatial variation of hydrocarbon molecules and dust surrounding the star. The rovibrational bands of acetylene (C 2 H 2 ) and hydrogen cyanide (HCN) at 3.0 lm are evident in the central star spectra. The molecules are concentrated in the compact region near the center. The 3.3 and 3.4 lm emission of aromatic and aliphatic hydrocarbons is detected at 600-1300 AU from the central star. The separation of spatial distribution between gas and dust suggests that the small hydrocarbon molecules are indeed the source of solid material and that the gas left over from the grain formation is being observed near the central star. The intensity of aliphatic hydrocarbon emission relative to the aromatic hydrocarbon emission decreases with distance from the central star. The spectral variation is well matched to that of a laboratory analog thermally annealed with different temperatures. We suggest that either the thermal process after the formation of a grain or the variation in the temperature in the dust-forming region over time determines the chemical composition of the hydrocarbon dust around the proto-planetary nebula.

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“…Various carbonaceous materials have been proposed as the UIR band carriers. In general, they can be divided into two classes: (1) free-flying aromatic molecules-polycyclic aromatic hydrocarbon molecules (PAHs; Léger & Puget 1984;Allamandola, Tielens, & Barker 1985); and (2) carbonaceous grains with a partly aromatic character-hydrogenated amorphous carbon (HAC; Duley & Williams 1981;Jones, Duley, & Williams 1990), quenched carbonaceous composite (QCC; Sakata et al 1990), coal (Papoular et al 1993), fullerenes (Webster 1993), and surface-graphitized nanodiamonds (Jones & d'Hendecourt 2000).…”

Section: Introductionmentioning

confidence: 99%

Do the Infrared Emission Features Need Ultraviolet Excitation? The Polycyclic Aromatic Hydrocarbon Model in UV‐poor Reflection Nebulae

Draine

2002

ApJ

145

120

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One of the major challenges to identification of the 3. 3, 6.2, 7.7, 8.6, and 11.3 lm interstellar infrared (IR) emission bands with polycyclic aromatic hydrocarbon (PAH) molecules has been the recent detection of these bands in regions with little ultraviolet (UV) illumination, since small, neutral PAH molecules have little or no absorption at visible wavelengths and therefore require UV photons for excitation. We show here that our '' astronomical '' PAH model, incorporating the experimental result that the visual absorption edge shifts to longer wavelength upon ionization and/or as the PAH size increases, can closely reproduce the observed IR emission bands of vdB 133, a UV-poor reflection nebula. We also show that single-photon heating of '' astronomical '' PAHs in reflection nebulae near stars as cool as T eff ¼ 3000 K can result in observable emission at 6.2, 7.7, 8.6, and 11.3 lm. Illustrative mid-IR emission spectra are calculated for reflection nebulae illuminated by cool stars with T eff

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Quenched carbonaceous composite. III - Comparison to the 3.29 micron interstellar emission feature

Cited by 42 publications

References 0 publications

$\mathsf{^{13}}$C isotope effects on infrared bands of quenched carbonaceous composite (QCC)

$\mathsf{^{13}}$C isotope effects on infrared bands of quenched carbonaceous composite (QCC)

Spatially Resolved 3 Micron Spectroscopy of IRAS 22272+5435: Formation and Evolution of Aliphatic Hydrocarbon Dust in Proto–Planetary Nebulae

Do the Infrared Emission Features Need Ultraviolet Excitation? The Polycyclic Aromatic Hydrocarbon Model in UV‐poor Reflection Nebulae

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