Astronomy and Astrophysics – Astrophysics
Scientific paper
Jun 1986
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1986apj...305..433s&link_type=abstract
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 305, June 1, 1986, p. 433-454.
Astronomy and Astrophysics
Astrophysics
14
Cosmic Dust, Grains, Impurities, Interstellar Matter, Optical Properties, Anomalies, Cores, Grain Size, Incident Radiation, Interstellar Extinction
Scientific paper
The scattering and absorption cross sections and extinction profiles of grains of arbitrary size compared with the wavelength of incident light are calculated for grains containing resonantly absorbing impurity atoms or molecules. Such grains are candidates for explaining the diffuse interstellar bands. The embedded cavity model of Purcell and Shapiro (1977) is used to derive the bulk dielectric constants of the composite grain material (host grain plus resonant impurities). These bulk dielectric constants are used to derive cross sections from Mie theory for homogeneous spherical grains and from the solution of Guttler (1952) for spherical core-mantle grains. An investigation is conducted so as to ascertain the effect on the grain extinction profiles of variations in such parameters as particle size, host grain composition, impurity oscillator strength, impurity concentration, and the confinement of the resonant impurities to a grain mantle or core. The present results for particle sizes comparable to or larger than the wavelength differ substantially from previous results obtained prior to the development of the embedded cavity model. Taken together with the differences already found by Purcell and Shapiro for small particle profiles, these results indicate that the extinction profiles can differ appreciably from previous predictions for grains of any size. Future attempts to match the observed characteristics of diffuse interstellar bands with theoretical dust grain extinction profiles must take these new results into account.
Holcomb Katherine Ann
Shapiro Paul R.
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