Infrared Spectroscopy of Diamondoid Molecules: New Insights into the Presence of Nanodiamonds in the Interstellar Medium

Pirali, Olivier; Vervloët, M.; Dahl, Jeremy E. P.; Carlson, Robert M. K.; Tielens, A. G. G. M.; Oomens, Jos

doi:10.1086/516731

Cited by 91 publications

(120 citation statements)

References 26 publications

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“…These sources are different from the ones previously discussed for the 21 "microns" feature. Recently, from a molecular approach, Pirali et al (2007) measured small diamondoids in the gas phase and, reported calculations, as well as attenuated total reflectance spectra for higher diamondoids. Analogues of the measured species with the same symmetry containing around 130 C atoms (e.g., C 136 H 104 ) show an intensity ratio of the 3.53 and 3.43 μm bands close to that observed in the interstellar spectra.…”

Section: (Nano-)diamondsmentioning

confidence: 99%

Observations of Interstellar Carbon Compounds

Dartois

2011

EAS Publications Series

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Abstract. Infrared absorption and emission features observed spectroscopically in our Galaxy allow to probe the composition of solid dust grains, their evolution and thus follow the cycling of matter in the Galaxy. Many observables do reveal the presence of large amounts of carbonaceous particles in space, other than the PAH-like emission lines. The carbonaceous materials observed include amorphous carbons, diamondoids showing in emission for a few specific sources, and the recently detected fullerenes. An important hydrogenated amorphous carbon component (HAC or a-C:H), traced by the 2940 cm −1 structured absorption feature is observed against Galactic background sources. Since the discovery of this feature in the early eighties (Allen 1981), the observation of a-C:H has been extended to the mid-infrared by space observatories, giving insight into additional associated features. They are also observed in external galaxies, showing the ubiquitous nature of these components. We will focus on astronomical observations of organic matter other than PAHs, amorphous carbons and associated laboratory dust analogues relevant to astrophysical applications.

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Section: (Nano-)diamondsmentioning

confidence: 99%

Observations of Interstellar Carbon Compounds

Dartois

2011

EAS Publications Series

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“…For example, adamantane (C 10 H 16 ), with a cage-like, full sp 3 structure, shows vibrational bands in the 3 µm region in both gas and solid phases (Oomens et al 2006;Pirali et al 2007). The C-H stretch of hydrogenated diamonds at 3.43 and 3.53 µm have been detected (Guillois, Ledoux, & Reynaud 1999).…”

Section: Introductionmentioning

confidence: 99%

On the Origin of the 3.3 μm Unidentified Infrared Emission Feature

Sadjadi

Zhang

Kwok

2017

ApJ

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The 3.3 µm unidentified infrared emission feature is commonly attributed to C-H stretching band of aromatic molecules. Astronomical observations have shown that this feature is composed of two separate bands at 3.28 and 3.30 µm and the origin of these two bands is unclear. In this paper, we perform vibrational analyses based on quantum mechanical calculations of 153 organic molecules, including both pure aromatic molecules and molecules with mixed aromatic/olefinic/aliphatic hydridizations. We find that many of the C-H stretching vibrational modes in polycyclic aromatic hydrocarbon (PAH) molecules are coupled. Even considering the un-coupled modes only, the correlation between the band intensity ratios and the structure of the PAH molecule is not observed and the 3.28 and 3.30 µm features cannot be directly interpreted in the PAH model. Based on these results, the possible aromatic, olefinic and aliphatic origins of the 3.3 µm feature are discussed. We suggest that the 3.28 µm feature is assigned to aromatic C-H stretch whereas the 3.30 µm feature is olefinic. From the ratio of these two features, the relative olefinic to aromatic content of the carrier can be determined.

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“…The hydrogenated solids comprise nanodiamonds, observed through vibration bands at 3.43 and 3.53 μm of hydrogen-terminated nanodiamonds (Chang et al 1995;Guillois et al 1999;Pirali et al 2007) in equilibrium with the stellar radiation field. They are observed close to the stars around very few objects (Habart et al 2004;Acke et al 2006;Goto et al 2009).…”

Section: Introductionmentioning

confidence: 99%

Vacuum ultraviolet photolysis of hydrogenated amorphous carbons

Alata

Cruz-Díaz

Muñoz

et al. 2014

A&A

119

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Context. The interstellar hydrogenated amorphous carbons (HAC or a-C:H) observed in the diffuse medium are expected to disappear in a few million years, according to the destruction time scale from laboratory measurements. The existence of a-C:H results from the equilibrium between photodesorption, radiolysis, hydrogenation and resilience of the carbonaceous network. During this processing, many species are therefore injected into the gas phase, in particular H 2 , but also small organic molecules, radicals or fragments. Aims. We perform experiments on interstellar a-C:H analogs to quantify the release of these species in the interstellar medium. Methods. The vacuum ultraviolet (VUV) photolysis of interstellar hydrogenated amorphous carbon analogs was performed at low (10 K) to ambient temperature, coupled to mass-spectrometry detection and temperature-programed desorption. Using deuterium isotopic substitution, the species produced were unambiguously separated from background contributions. Results. The VUV photolysis of hydrogenated amorphous carbons leads to the efficient production of H 2 molecules, but also to small hydrocarbons. Conclusions. These species are formed predominantly in the bulk of the a-C:H analog carbonaceous network, in addition to the surface formation. Compared with species made by the recombination of H atoms and physisorbed on surfaces, they diffuse out at higher temperatures. In addition to the efficient production rate, it provides a significant formation route in environments where the short residence time scale for H atoms inhibits H 2 formation on the surface, such as PDRs. The photolytic bulk production of H 2 with carbonaceous hydrogenated amorphous carbon dust grains can provide a very large portion of the contribution to the H 2 molecule formation. These dust grains also release small hydrocarbons (such as CH 4 ) into the diffuse interstellar medium, which contribute to the formation of small carbonaceous radicals after being dissociated by the UV photons in the considered environment. This extends the interstellar media environments where H 2 and small hydrocarbons can be produced.

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Infrared Spectroscopy of Diamondoid Molecules: New Insights into the Presence of Nanodiamonds in the Interstellar Medium

Cited by 91 publications

References 26 publications

Observations of Interstellar Carbon Compounds

Observations of Interstellar Carbon Compounds

On the Origin of the 3.3 μm Unidentified Infrared Emission Feature

Vacuum ultraviolet photolysis of hydrogenated amorphous carbons

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