Matsushima F, Odashima H, Iwasaki T, Tsunekawa S, Takagi K. Frequency measurement of pure rotational transitions of H2O from 0.5 to 5 THz. In: Conference on precision electromagnetic measurements digest.; 1994. p. 23–4.
Abstract: Frequencies of H2O pure rotational transitions from 0.5 to 5 THz have been measured with an accuracy of one part in 109 using a tunable far-infrared spectrometer. Measured frequencies of more than a hundred spectral lines provide an excellent wavelength and frequency calibration standard for the far infrared.