The Densities of Charged Particles in Very Dense Interstellar Clouds

概要

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We examine the following processes on the grain surface: the adsorption of ions and electrons to the surface; the recombination of ions and electrons at grain-ion, grain-electron and grain-grain collisions; and desorption of ions and electrons from the surface. As the temperature increases, the sticking probability of electrons to the surface is found to decrease to 0.1 or lower, while that of ions remains very close to unity. Above a certain critical temperature around several hundred kelvin, the desorption becomes abruptly efficient. Solving the rate equations for the chemical and grain-surface reactions, we investigate the abundances of various charged particles in very dense interstellar clouds (protostars). As long as the desorption is inefficient, grains with one excess ion and with one excess electron are the major constituents among charged particles at densities higher than 10^<10>cm^<-3>. Unlike the cases at lower densities, electrons and metal ions in the gas phase are only minor constituents, and it is found that the abundance of electrons is about 200 times smaller than that of metal ions. When the desorption becomes efficient, electrons and ions in the gas phase increase extensively as charged grains decrease. At the temperature above about 10^3K the thermal ionization dominates over the other processes of ionization, and the ionization degree increases extensively with the temperature.
理論物理学刊行会の論文
1983-02-25