On the Electronic Structure of Small Carbon Grains of Astrophysical Interest

Details On the Electronic Structure of Small Carbon Grains of Astrophysical Interest On the Electronic Structure of Small Carbon Grains of Astrophysical Interest

Sep 1995

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995apjs..100..149m&link_type=abstract

Astrophysical Journal Supplement v.100, p.149

Astronomy and Astrophysics

Astronomy

40

Stars: Circumstellar Matter, Ism: Dust, Extinction, Stars: Carbon, Methods: Laboratory, Ultraviolet: Ism

Scientific paper

In a previous paper Mennella et al. (l995a) studied the evolution of the UV spectrum of small carbon grains due to thermal annealing in the range 250-800°C. The spectral variations were interpreted in terms of internal structural rearrangement of the grains caused by hydrogen loss. The electronic transitions (σ-σ* and π-π*) of the sp2 clusters forming the grains were indicated as the major factors responsible for determining their extinction properties.
In this paper we present the results of new measurements aimed at probing the heat-induced structural changes. The thermal evolution of the optical gap and of the Raman spectrum, both sensitive to the sp2 clustering degree, confirms that the observed spectral changes do depend on structural variations. In fact, the π electron delocalization of the sp2 clusters determines a link between structural and electronic properties in carbons.
We find a basic correlation between the UV peak position and the optical gap. It is interpreted in terms of a dependence of the dipole matrix momentum of π transitions on the sp2 cluster size.
The attribution of the spectral changes to the grain internal structure is corroborated by morphological analyses. Scanning and transmission electron microscope images show that the fluffy structure of the samples as well as the dimension and the shape of the single grains do not change after the annealing process.
In the astrophysical context, the present results can be relevant for the attribution of the 217.5 nm feature, as they show that the internal structure of carbon grains, having sizes similar to those expected for the "bump" carriers, controls the interaction with UV photons.

Affiliated with

Also associated with

No associations

Rating

On the Electronic Structure of Small Carbon Grains of Astrophysical Interest does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with On the Electronic Structure of Small Carbon Grains of Astrophysical Interest, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and On the Electronic Structure of Small Carbon Grains of Astrophysical Interest will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-824898