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Astron. Astrophys. 336, L41-L44 (1998)
Letter to the Editor
Diamonds in carbon-rich proto-planetary nebulae
H.G.M. Hill
* 1, 2,
A.P. Jones 2 and
L.B. d'Hendecourt 2
1 Muséum National d'Histoire Naturelle, 61 Rue
Buffon, F-75005 Paris, France
2 Institut d'Astrophysique Spatiale (CNRS),
Université Paris XI - Bâtiment 121, F-91405 Orsay Cedex,
France
Received 23 December 1997 / Accepted 16 June 1998
Abstract
We present the results of a mid-infrared laboratory study of
meteoritic nanodiamonds, a natural `nitro-gen-rich' terrestrial
diamond, and a `nitrogen-poor' diamond before and after irradiation
with fast neutrons. Characteristic one-phonon modes, absent in the
perfect diamond structure, are evident in the `nitrogen-rich' and
neutron-irradiated diamonds that we analysed. One feature common to
these bulk materials occurs at
![[FORMULA]](img1.gif)
21 µm. The precise origin of this
feature is unknown, although it may arise from molecular-type
vibrations associated with lattice defects created by nitrogen
impurities or neutron irradiation. We suggest that interstellar
nanodiamonds also possess this feature and that they are the carrier
of the unidentified 21 µm infrared
emission feature observed in the dust shells around some carbon-rich
proto-planetary nebulae.
Key words: Stars: AGB and post-AGB, carbon, circumstellar
matter 
Interstellar Medium: dust, emission,
extinction
Interstellar Medium: general
* Correspondence to email address: hill@mnhn.fr
Contents
- 1. Introduction
- 2. Infrared spectroscopy of diamonds
- 3. Astrophysical implications
- 4. Conclusions
- Acknowledgements
- References
© European Southern Observatory (ESO) 1998
Online publication: July 27, 1998
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