The calculated ν2 (inversion) spectrum of H3O+

Abstract
We report the observation and assignment of a number of vibration–rotation transitions within 1←1+ band of H3O+. The data are analyzed together with previously published measurements to yield a consistent set of rotational parameters that accurately reflects the vibration–rotation spectra involving the four lowest levels associated with the ν2 vibration of the ion. The analysis enables a precise estimate of the inversion splitting and the associated inversion‐rotation spectrum of H3O+ which occurs in the far infrared.