Graphene Molecule Compared With Fullerene C60 As Circumstellar Carbon Dust Of Planetary Nebula

TL;DR

This study uses quantum-chemical calculations to compare graphene and fullerene C60 as potential carriers of infrared emission features in carbon-rich planetary nebulae, highlighting graphene's significant role.

Contribution

It demonstrates that graphene-based molecules can reproduce observed infrared spectra better than fullerene C60 in astrophysical conditions.

Findings

Graphene-related molecules reproduce major infrared bands from 6 to 38 micrometers.

Void-induced molecules like C23, C22, and C21 support observed spectral features.

Graphene plays a more significant role than fullerene C60 in circumstellar dust emission.

Abstract

It had been understood that astronomically observed infrared spectrum of carbon rich planetary nebula as like Tc 1 and Lin 49 comes from fullerene (C60). Also, it is well known that graphene is a raw material for synthesizing fullerene. This study seeks some capability of graphene based on the quantum-chemical DFT calculation. It was demonstrated that graphene plays major role rather than fullerene. We applied two astrophysical conditions, which are void creation by high speed proton and photo-ionization by the central star. Model molecule was ionized void-graphene (C23) having one carbon pentagon combined with hexagons. By molecular vibrational analysis, we could reproduce six major bands from 6 to 9 micrometer, large peak at 12.8, and largest peak at 19.0. Also, many minor bands could be reproduced from 6 to 38 micrometer. Also, deeply void induced molecules (C22) and (C21) could support observed bands.