Detection of NH3Molecules in the Interstellar Medium by Their Microwave Emission

Ammonia has been found in the direction of the galactic center by detection of its $J=1\mathrm{}$, $K=1\mathrm{}$ inversion transition. The region of emission closely corresponds to the position, velocity, and size of strong OH absorption. Collisional and radiative excitation mechanisms are discussed. The column density of N${\mathrm{H}}_3$ and the kinetic temperature of the interstellar gas cloud are estimated to be 2×${10}^{16}$/${\mathrm{cm}}^2$ and 23°K, respectively.