Radio Observations of Hydrogen II Regions in the Galactic Center.

Observations of radio recombination lines allow sources which lie along the line of sight to be distinguished from those in the galactic center. The separation is based on the radial velocities and widths of the lines. The galactic center lines arise in discrete sources and an extended thermal source. The discrete H regions are all at positive longitudes. The extended source appears to rotate as a rigid body and is neither expanding nor contracting. The extended source differs in this respect from the clouds of H2CO and OH, which appear to form rotating and expanding rings. Within 15 arc min of Sgr A the kinematics of the ionized gas changes. Most of the lines from this region have negative velocities, but little systematic behavior is apparent. High resolution observations of CO show no correlation with the recombination lines.