Invited review article for "Astrophysics of Dust"
Symposium (Estes Park, Colorado, USA; May 26-30, 2003), ed. A.N. Witt,
G.C. Clayton, and B.T. Draine.
astro-ph/0311066
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INTERACTION OF NANOPARTICLES WITH RADIATION
Aigen Li
Theoretical Astrophysics Program,
The University of
Arizona,
Tucson, AZ 85721;
agli@lpl.arizona.edu
Abstract.
Interstellar grains span a wide range of sizes
from a few angstroms to a few micrometers.
The presence of nanometer-sized or smaller particles
in the interstellar medium is indicated directly by
the interstellar far ultraviolet (UV) extinction,
the ubiquitous 3.3, 6.2, 7.7, 8.6, and 11.3 µm
polycyclic aromatic hydrocarbon (PAH) emission features,
the near and mid infrared broadband emission seen in
the IRAS 12 and 25 µm bands and the COBE-DIRBE
3.5, 4.9, 12 and 25 µm bands, the 10-100 GHz
Galactic foreground microwave emission,
and indirectly by the heating of interstellar gas.
For nanoparticles under interstellar conditions,
UV/visible photon absorption is the dominant
excitation process.
With a heat capacity smaller than or comparable to the energy
of an energetic stellar photon, nanoparticles are subject
to single-photon heating, followed by vibrational relaxation,
photoionization, and photodestruction.
With excited electrons spatially confined,
semiconductor nanoparticles are expected to
luminesce efficiently.
This review focuses on the photophysics of nanoparticles
with emphasis on the stochastic heating and the vibrational
excitation of interstellar PAH molecules,
and the excitation of photoluminescence
with special attention given to silicon nanoparticles.
Table of Contents
INTRODUCTION: Historical Perspectives of Studies of
Interstellar Grain Compositions and Sizes
- NANOPARTICLES IN INTERSTELLAR SPACE
- EXCITATION OF VIBRATIONAL TRANSITIONS
- An Overview of the Photoexcitation and Emission
Processes
- "Exact-Statistical" Approach
- "Thermal" Approach
- EXCITATION OF PHOTOLUMINESCENCE
- AN OVERVIEW OF INTERSTELLAR NANOPARTICLE SPECIES
- Nano Carbon Grains: Polycyclic Aromatic Hydrocarbon
Dust
- Nano Silicate Grains
- Nano Silicon Grains
- Nano Diamond Grains
- Nano Titanium Carbide Grains
- CONCLUDING REMARKS
- REFERENCES
