RO-INVERSIONAL SPECTRUM OF AMMONIA

The ground state J = 2 <-- 1, K = 0 and K = 1 ro-inversional spectrum of (NH3)-N-14 and (NH3)-N-15;It 1.2 THz has been measured with an accu racy of 20 kHz using the Cologne terahertz spectrometer. The measured frequencies for the K = 0 components are: (NH3)-N-14 (J, K) = a(2, 0) - s(1, 0): 1 214 852.942(20) MHz, (NH3)-N-15 (J, K) = a(2, 0) - s(1, 0 ): 1 210 889.556(20) MHz. In addition we have determined from saturati on dip measurements of the J = 1-0 transition the spin-rotation consta nt C-N = 6.7(3) kHz and the unsplit line center frequency: (NH3)-N-14 (J, K) = s(1, 0) - a(0, 0): 572 498.163(10) MHz. The new results are i n excellent agreement with existing high resolution Fourier transform data. The terahertz line frequencies are of considerably higher accura cy than the FT-data, by about two orders of magnitude. They will serve as future calibration lines. The ro-inversional transitions are of as trophysical interest.