HIGH-RESOLUTION OBSERVATIONS OF A NEW AMMONIA MASER LINE IN G9.62+0.19

We present interferometric observations of the NH3(5,5) inversion line toward the H II region complex G9.62 + 0.19 which confirm the discovery of maser action in this transition. At the present time G9.62 + 0.19 is the only known source where this maser occurs. The maser is unresolved; an upper limit to its size is 0.5'' corresponding to a lower limit on the brightness temperature of 10(4) K. The NH3(5,5) maser is coincident with a weak continuum source and a water maser. Emission from thermal ammonia consisting of two clumps is detected almost-equal-to 8'' south of the maser position. The thermal ammonia clumps are elongated toward the position of the NH3(5,5) maser and form part of a linear structure of length almost-equal-to 0.6 pc, outlined by maser emission in several molecular lines, highly excited ammonia and ultracompact H II regions.