Abstract

Two techniques for rotational analysis of the nd1b1 Rydberg spectra of H2O and D2O are discussed—a Coriolis coupled asymmetric top model for the room temperature 3d1b1 cluster, and an extension of multichannel quantum defect theory to asymmetric tops, which is applied to recent jet cooled photoionization spectra of the nd1b1 series converging to the (100) vibrational levels of H2O+ and D2O+. The quantum defects obtained by the two methods are in good agreement and new ionization limits to the (100) series are derived: IP(100) = 104985(2) cm−1 for H2O and 104262(1) cm−1 for D2O.