A comparison of solid-state carbonaceous models of cosmic dust
R. Papoular, J. Conard, O. Guillois, I. Nenner, C. Reynaud, J. N. Rouzaud;
AaA, 1996, 315, 222
ABSTRACT:This is a tentative synopsis of available results from laboratories specialized in solid carbon research related to cosmic dust.
Differences and
similarities between materials proposed as dust models are highlighted so as to
clarify the term "amorphous carbon", which is often used to designate very
different products.
These materials were tentatively related to a-C:H and
coals, which have been, for decades, and are still being, studied with the most
sophisticated experimental methods.
The physical understanding that has been
reached in these fields makes it possible now to group together some of the
proposed materials in 3 classes according to their gross structural and optical
properties, and, hence, to the part they may play in modelling astrophysical
observations, which no one of them can do entirely by itself.
These are: a)
polygranular graphite; b) coals and oxidized, heat treated, f-QCC (a-C:H, HAC); c)
glassy carbon grains such as carbon arc particles (TU, AC-Ar) and annealed
soot from hydrocarbon flames (XY, BE, AC-H2).
Their respective preferred
fields of modelling applications seem to be: a) the UV bump and FUV rise of IS
extinction curves; b) the Unidentified Infrared Bands (UIBs), the Extended Red
Emission (ERE)and interstellar (IS) IR extinction; c) the UV bump in extinction
by the circumstellar dust of a number of stars.
The role of heat
treatment, which is often used to improve the fits to astronomical observations,
is discussed.
More generally, the present degree of physical
understanding of carbon structure may help improving the proposed models through
appropriate physical and chemical treatment.
KEYWORDS: dust: extinction, molecular data, infrared: ism: lines and bands
CODE: papoular96