A highly excited ammonia cloud at least 300 PC from the galactic centre.

Using the 100-m Effelsberg telescope, a cloud with a LSR velocity of about 160 km/s and a half-width of about 25 km/s was mapped in the (1,1), (2,2), and (4,4) lines of para NH3 and the (3,3) and (6,6) lines of ortho NH3. The high temperatures obtained may result from collisions with H2 in excited states. It is suggested that the cloud may be located near the periphery of the rotating nuclear disk where conditions would be favorable for the production of shocks, excited H2, and possible high NH3 temperatures.