Abstract
In molecular clouds the dust charge can be determined by non-thermal electrons from cosmic-ray ionization. If the energy of the non-thermal electrons is E≥2 keV and their fraction is only 10−3–10−4 of the thermal electrons in a molecular gas, the grain charge can be as high as | z | ≈ 10 in the range of gas densities n≈ 105–106 cm−3. In the high-density range n>106 cm−3, the grain charge approaches the thermal limit | z | ≈ 0.3.
Acknowledgements
This work was supported by the Federal Agency of Education (project code RNP 2.1.1.3483), by the Russian Foundation for Basic Research (project codes 05-02-17070 and 06-02-16819) and by the Deutsche Forschungsgemeinschaft within Sonderforschungsbereich 591 TP A6.