Abstract
ONE of us has shown1,2 that the interstellar extinction curve in the visible spectral region may be represented to a high degree of accuracy by two straight lines intersecting at λ = 4300 Å. Although graphite flakes or graphite cores with dielectric mantles come close to fitting the observational curve3, it is clearly not possible to explain a very sharp knee on the basis of Mie scattering by solid particles. The role of impurity induced absorption bands has been discussed recently4,5 in connexion with the 4430 å absorption band. The most widely studied impurity bands are the so-called F centres6,7 in alkali halides which occur in the visible and near ultraviolet. Fig. 1 shows a typical absorption profile due to an F centre in KBr (ref. 7). Such a band, which could occur in any crystalline solid at a wavelength defined by the lattice, is caused by electrons trapped at vacancies. Features common to all such bands are: (a) f values close to unity; (b) symmetrical profiles; (c) widths of the order 1000 Å. We have already suggested5 that such a broad diffuse absorption band may be present, but escape resolution in stellar spectra. We consider here the possibility that the knee in the interstellar extinction at λ = 4300 Å may be caused by such a band superposed on the extinction curve derived from Mie scattering.
This is a preview of subscription content, access via your institution
Access options
Subscribe to this journal
Receive 51 print issues and online access
$199.00 per year
only $3.90 per issue
Buy this article
- Purchase on Springer Link
- Instant access to full article PDF
Prices may be subject to local taxes which are calculated during checkout
Similar content being viewed by others
References
Nandy, K., Pub. Roy. Obs. Edin., 3, 142 (1964).
Nandy, K., Pub. Roy. Obs. Edin. (in the press).
Nandy, K., and Wickramasinghe, N. C., Pub. Roy. Obs. Edin., 5, 29 (1965).
Hoyle, F., and Wickramasinghe, N. C., Nature, 214, 969 (1967).
Wickramasinghe, N. C., Ireland, J. G., Nandy, K., Seddon, H., and Wolstencroft, R. D., Nature, 217, 412 (1968).
Ivey, H. F., Phys. Rev., 72, 341 (1947).
Schulman, J. H., and Compton, W. D., Colour Centres in Solids (Macmillan Co., New York, 1962).
Wickramasinghe, N. C., Interstellar Grains (Chapman and Hall, Ltd, London, 1967).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
NANDY, K., SEDDON, H., WOLSTENCROFT, R. et al. Colour Centres in Interstellar Grains. Nature 218, 1236–1237 (1968). https://doi.org/10.1038/2181236a0
Received:
Issue Date:
DOI: https://doi.org/10.1038/2181236a0
This article is cited by
-
On the nature of interstellar grains
Astrophysics and Space Science (1979)
-
Origin of broad interstellar feature at 1.6 µm−1
Nature (1975)
-
Profiles of the diffuse interstellar lines
Astrophysics and Space Science (1972)
Comments
By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.