We present observations of the { NH _ { 3 } } ( J , K ) = ( 1,1 ) and ( 2,2 ) inversion transitions toward the infrared dark cloud G28.34+0.06 , using the Very Large Array .
Strong { NH _ { 3 } } emission is found to coincide well with the infrared absorption feature in this cloud .
The northern region of G28.34+0.06 is dominated by a compact clump ( P2 ) with a high rotation temperature ( 29 K ) , large line width ( 4.3 km s ^ { -1 } ) , and is associated with strong water maser ( 240 Jy ) and a 24 \mu m point source with far IR luminosity of 10 ^ { 3 } L _ { \odot } .
We infer that P2 has embedded massive protostars although it lies in the 8 \mu m absorption region .
The southern region has filamentary structures .
The rotation temperature in the southern region decreases with the increase of the integrated { NH _ { 3 } } intensity , which indicates an absence of strong internal heating in these clumps .
In addition , the compact core P1 in the south has small line width ( 1.2 km s ^ { -1 } ) surrounded by extended emission with larger line width ( 1.8 km s ^ { -1 } ) , which suggests a dissipation of turbulence in the dense part of the cloud .
Thus , we suggest that P1 is at a much earlier evolutionary stage than P2 , possibly at a stage that begins to form a cluster with massive stars .