Chemical Equilibrium of Dust at Low Temperature
Abstract
The opacity of material is required whenever the detailed transfer of radiation through a gas is modeled. Computation of the opacity requires both a thorough knowledge of the chemical state of the gas (species populations) and the absorption/scattering behavior of those species. At low temperatures the equation of state (EOS) calculations become particularly complex. Our EOS computations assume chemical equilibrium and include over 600 solid and liquid species with data mainly from the JANAF database. We will present and discuss our EOS computations for gas temperatures from 2000 K to 300 K and a wide range of gas densities, pressures and chemical compositions. Large discontinuities in species abundances are seen when an individual grain species condenses. It has been known for some time that solid silicate and iron particles play important roles in the chemical equilibrium and opacity of a cool gas. Many other condensed species, including Al2 O3, CaTiO3, and even carbon at very low temperature, can play equally important roles.
- Publication:
-
Astrophysics of Dust
- Pub Date:
- 2003
- Bibcode:
- 2003asdu.confE.127F