SUB-MILLIMETRE DISPERSION ROTATIONAL LINE STRENGTHS AND DIPOLE MOMENT OF GASEOUS AMMONIA

Using the technique of Fourier spectrometry the refractive index spectrum of gaseous ammonia has been observed from 15 to 116 cm-1 (667 to 87 μm). The integrated absorption strengths of the rotational lines (J + 1) ← J for J = 0 to J = 4 have been evaluated from the anomalous dispersion data. A value μ = 1·48 ± 0·06 D has been calculated for the electric dipole moment of the ammonia molecule. In an assessment of accuracy, dipole moment parameters obtained from Fourier dispersion studies of gaseous HCl, HBr and HI are also considered to show that there is no evidence for a systematic error inherent in this method for finding absorption strengths. © 1969.