THERMAL-PROCESSING OF CARBON DUST AROUND A COOL STAR

Thermal-processed carbonaceous materials could emulate the evolution of the carbonaceous dust which settles in
regions around a cool star in a proto-planetary nebula (PPN). Spectroscopically, this evolution has been shown through the
variation in the strength of the aliphatic (-C-H stretching mode at the 3.42 μm) band relative to those of the aromatic (=C-H
mode at the 3.3 μm) band. Experimentally, the laser ablation technique was used to produce the Hydrogenated Amorphous
Carbon (HAC) samples as analogs of comic carbon dust. The IR-laboratory data of these samples shows that the strength of
these two bands varies reversely to each other as HAC transforms from the aliphatic to aromatic structure with heating. The
temperature, required to cause this transformation within HAC, depends on its hydrogen content. Hence, the trend of this variation
is also in relevance to the hydrogen content within HAC. This trend shows the variation from the aliphatic to aromatic
structure in dust grains in regions within the PPN IRAS 22272+5435. In which, it is expected that dust grains may be heated
in the past in the warm region near the star.