Graphitic network models of ‘‘diamondlike’’ carbon

Tamor, M. A.; Wu, C. H.

doi:10.1063/1.345808

Cited by 172 publications

(68 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We used the aromatic H/C ratio and aromatic+aliphatic H/C ratio, presented as two linear fits for the hydrogen poor (low E g ) regime (only soots). When both aromatic and aliphatic CH modes are included, our linear fit approaches the coefficient found for amorphous carbon in Tamor & Wu (1990). The shape of the symbols corresponds to those used in Fig.…”

Section: H/c Ratiossupporting

confidence: 52%

Polyaromatic disordered carbon grains as carriers of the UV bump: Far-UV to mid-IR spectroscopy of laboratory analogs

Gavilan

Pino

et al. 2017

A&A

View full text Add to dashboard Cite

Context. A multiwavelength study of laboratory carbons with varying degrees of hydrogenation and sp 2 hybridization is required to characterize the structure of the carbonaceous carriers of interstellar and circumstellar extinction. Aims. We study the spectral properties of carbonaceous dust analogs from the far-ultraviolet to the mid-infrared and correlate features in both spectral ranges to the aromatic/aliphatic degree. Methods. Analogs to carbonaceous interstellar dust encountered in various phases of the interstellar medium have been prepared in the laboratory. These are amorphous hydrogenated carbons (a-C:H), analogs to the diffuse interstellar medium component, and soot particles, analogs to the polyaromatic component. Thin films (d < 100 nm) have been measured in transmission in the vacuumultraviolet (VUV; 120-210 nm) within the atmospheric pressure experiment (APEX) chamber of the DISCO beam line at the SOLEIL synchrotron radiation facility. Spectra of these films were further measured through the UV-Vis (210 nm-1 µm) and in the mid-infrared (3-15 µm). Results. Tauc optical gaps, E g , are derived from the visible spectra. The major spectral features are fitted through the VUV to the midinfrared to obtain positions, full-widths at half maximum (FWHM), and integrated intensities. These are plotted against the position of the π-π * electronic transitions peak. Unidentified or overlapping features in the UV are identified by correlations with complementary infrared data. A correlation between the optical gap and position of the π-π * electronic transitions peak is found. The latter is also correlated to the position of the sp 3 carbon defect band at ∼8 µm, the aromatic C=C stretching mode position at ∼6 µm, and the H/C ratio. Conclusions. Ultraviolet and infrared spectroscopy of structurally diverse carbon samples are used to constrain the nanostructural properties of carbon carriers of both circumstellar and interstellar extinction, such as the associated coherent lengths and the size of polyaromatic units. Our study suggests that carriers of the interstellar UV bump should exhibit infrared bands akin to the A/B classes of the aromatic infrared bands, while the circumstellar bump carriers should exhibit bands corresponding to the B/C classes.

show abstract

Section: H/c Ratiossupporting

confidence: 52%

Polyaromatic disordered carbon grains as carriers of the UV bump: Far-UV to mid-IR spectroscopy of laboratory analogs

Gavilan

Pino

et al. 2017

A&A

View full text Add to dashboard Cite

show abstract

“…Hence, until such time as the gaps have been filled we rely upon a recentlydeveloped set of optical properties for a large part of the a-C(:H) family parameter space (Jones 2012a,b,c). These optical properties were built ground-up using random covalent network (RCN) models (Phillips 1979;Döhler et al 1980;Thorpe 1983;Angus & Jansen 1988) and extensions thereof (extended RCN (eRCN) and Defective Graphite (DG) models, Tamor & Wu 1990;Jones 1990Jones , 2012a to construct a solid-state framework method to derive their structure and thence their complex indices of refraction. This approach determines the compositionand size-dependent optical properties of a-C(:H) materials (the optEC (s) and optEC (s) (a) datasets, Jones 2012a,b,c) based upon eRCN and DG modelling methods (Jones 1990(Jones , 2012a.…”

Section: Hydrogenated Amorphous Carbons A-c(:h)mentioning

confidence: 99%

“…Hydrogenated amorphous carbon materials, a-C(:H), are macroscopically-structured, contiguous network, solid-state materials comprised of only carbon and hydrogen atoms. The properties of a-C(:H) materials have been well-studied within both the physics and astrophysics communities (e.g., Phillips 1979;Döhler et al 1980;Thorpe 1983;Robertson 1986Robertson , 1988Robertson , 1991Robertson , 2001Robertson , 2002Robertson & O'Reilly 1987;Angus & Jansen 1988;Angus & Hayman 1988;Tamor & Wu 1990;Mennella et al 1995Mennella et al , 1996Mennella et al , 2003Ferrari & Robertson 2000Kassavetis et al 2007;Llamas-Jansa et al 2007;Mennella 2008;Gadallah et al 2011;Jones 2012a,b,c).…”

Section: Hydrogenated Amorphous Carbons A-c(:h)mentioning

confidence: 99%

The global dust modelling framework THEMIS

Jones

Koehler

Ysard

et al. 2017

A&A

257

345

View full text Add to dashboard Cite

Here we introduce the interstellar dust modelling framework THEMIS (The Heterogeneous dust Evolution Model for Interstellar Solids), which takes a global view of dust and its evolution in response to the local conditions in interstellar media. This approach is built upon a core model that was developed to explain the dust extinction and emission in the diffuse interstellar medium. The model was then further developed to self-consistently include the effects of dust evolution in the transition to denser regions. The THEMIS approach is under continuous development and we are currently extending the framework to explore the implications of dust evolution in HII regions and the photon-dominated regions associated with star formation. We provide links to the THEMIS, DustEM and DustPedia websites where more information about the model, its input data and applications can be found.

show abstract

“…For these truly amorphous materials it turns out that it is medium-range, rather than shortrange, order that determines the band gap (Robertson 1986). Laboratory studies of amorphous hydrocarbons show that there is a linear relationship between the band gap of these materials and their hydrocarbon content (Tamor & Wu 1990)…”

Section: The Optical Properties Of Hydrogenated Amorphous Carbonsmentioning

confidence: 99%

Variations on a theme – the evolution of hydrocarbon solids

Jones

2012

A&A

View full text Add to dashboard Cite

Context. The properties of hydrogenated amorphous carbon (a-C:H) dust are known to evolve in response to the local conditions. Aims. We present an adaptable model for the determination of the optical properties of low-temperature, interstellar a-C:H grains that is based on the fundamental physics of their composition. Methods. The imaginary part of the refractive index, k, for a-C:H materials, from 50 eV to cm wavelengths, is derived and the real part, n, of the refractive index is then calculated using the Kramers-Kronig relations. Results. The formulated optEC (s) model allows a determination of the complex dielectric function, , and refractive index, m(n, k), for a-C:H materials as a continuous function the band gap, E g , which is shown to lie in the range −0.1 to 2.7 eV. We provide expressions that enable a determination of their optical constants and tabulate m(n, k, E g ) for 14 different values of E g . We explore the evolution of the likely extinction and emission behaviours of a-C:H grains and estimate the relevant transformation time-scales. Conclusions. With the optEC (s) model we are able to predict how the optical properties of an a-C:H dust component in the interstellar medium will evolve in response to, principally, the local interstellar radiation field. The evolution of a-C:H materials appears to be consistent with many dust extinction, absorption, scattering and emission properties, and also with H 2 molecule, daughter "PAH" and hydrocarbon molecule formation resulting from its photo-driven decomposition.

show abstract

Graphitic network models of ‘‘diamondlike’’ carbon

Cited by 172 publications

References 14 publications

Polyaromatic disordered carbon grains as carriers of the UV bump: Far-UV to mid-IR spectroscopy of laboratory analogs

Polyaromatic disordered carbon grains as carriers of the UV bump: Far-UV to mid-IR spectroscopy of laboratory analogs

The global dust modelling framework THEMIS

Variations on a theme – the evolution of hydrocarbon solids

Contact Info

Product

Resources

About