Electrons in the Interstellar Medium

A brief review is given of processes which cool electrons in dark clouds following their initial production through cosmic ray ionization of H2. Experimental data are presented which show that polar species, such as H2O, may be effective in cooling of electrons which have fallen below an energy of ~100 meV. Some very recent results suggest that cold electrons are free to penetrate amorphous dense water ice and it is suggested that these electrons may instigate solid state chemistry in ice mantles.