The Fractional Ionization in Dense Interstellar Clouds

Abstract

It is pointed out that charge-transfer reactions of complex molecular ions with neutral metal atoms significantly increase the fractional ionization in a dense interstellar cloud bombarded by high-energy cosmic rays. The mean time for ambipolar diffusion becomes comparable to the cloud lifetime only when densities exceed 106 cm -3 and the magnetic field will retard the gravitational collapse of clouds of smaller particle density. A brief discussion is given of some other consequences of the relatively high fractional ionization. Subject headings: abundances, nebular - atomic processes - interstellar matter - molecules, interstellar