This paper lists, in order of increasing value, the "B" rotational constants of most of the linear and symmetric top molecules which have been observed by microwave spectroscopy. Also are listed the microwave spectral lines which have been observed for the asymmetric tops water and formaldehyde. These data are useful for making a quick selection of a molecule which has a spectral line close to some previously selected frequency.
Keywords: Asymmetric, linear, and symmetric top molecules; formaldehyde; microwave spectra; spectral lines; water; “B” rotational constants.