The submillimeter-wave spectrum of the formaldehyde isotopomer (H2CO)-O-18in its ground vibrational state

The ground state rotational spectrum of (H2CO)-O-18 has been studied betwee n 485 and 835 GHz with a sample of natural isotopic composition. Additional lines have been recorded around 130 GHz and near 1.85 THz, using a recentl y developed far-infrared laser-sideband spectrometer. The accurate new line frequencies were fit together with previously published data to obtain gre atly improved spectroscopic constants. Both Watson's S and A reduced Hamilt onians have been employed yielding the rotational constants A(S) = 281 961. 215 (82), B-S = 36 902.275 51 (36), C-S = 32 513.405 89 (36), A(A) = 281 96 1.371 (82), B-A = 36 904.173 32 (91), and C-A = 32 511.524 65 (86) MHz, res pectively.