Astronomy and Astrophysics – Astronomy
Scientific paper
Sep 1998
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998apj...504l.113d&link_type=abstract
Astrophysical Journal Letters v.504, p.L113
Astronomy and Astrophysics
Astronomy
2
Ism: Molecules, Ism: Dust, Extinction, Infrared: Ism: Lines And Bands, Cosmology: Cosmic Microwave Background
Scientific paper
Infrared emission from very small graphite grains under conditions of temperature spiking using both quantized emission and absorption algorithms has been investigated. Quantization of the emission process, which has not been previously considered, shows that the internal or lattice temperature of such grains can be reduced to T<2.7 K on a transient basis. This occurs when the total energy content of the particle is ~0.1 eV, and emission of a single IR photon removes this energy. We find that this condition occurs in graphite particles with radii in the 10-50 A range when their temperature falls to ~20 K. A similar effect is also expected in nongraphitic particles when their energy content reaches that of an infrared photon in the 5-20 mu m range. On average, ~1%-1.5% of graphite particles with radii in this range would have T<2.7 K. In addition, a subset of these may be transiently at 0 K. Such very cold grains will be present in diffuse and, to some extent, in dark clouds and could be detected through long-wavelength absorption against the cosmic microwave background.
Duley Walter W.
Poole Gregory
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