Structure of the Alkali Hydroxides. I. Microwave Spectrum of Gaseous CsOH

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Abstract
The microwave spectra of gaseous CsOH and CsOD have been studied in a high‐temperature spectrometer. The spectrum indicates a linear or near‐linear molecule with a large‐amplitude, low‐frequency bending vibration. A large number of excited states involving the bending mode and the Cs–O stretching mode have been identified. The rotational constant Bv shows an unusual variation as the bending mode is excited; the cause is not yet understood. The Cs–O bond length is found to be 2.40±0.01 Å and the O–H distance is probably about 0.97 Å. The electric dipole moment is 7.1±0.5 D. Relative intensity measurements indicate a Cs–O stretching frequency of 400±80 cm−1 and a bending frequency in the neighborhood of 300 cm−1. All of the evidence supports a highly ionic cesium—oxygen bond.