Quantitative characterization of the water trimer torsional manifold by terahertz laser spectroscopy and theoretical analysis. II. (H2O)3

We report the measurement of two new (H2O)3 bands by terahertz laser vibration–rotation–tunneling (VRT) spectroscopy. Both bands have been assigned to torsional (“pseudorotational”) transitions and are highly perturbed by Coriolis interactions. The 42.9 cm−1 band corresponds to the k=±2←±1 transition while the 65.6 cm−1 band corresponds to the k=±2←0 transition. A model Hamiltonian is derived which allowed a global fit of 361 VRT transitions of these two new bands and the previously reported torsional band at 87.1 cm−1. Each of the bifurcation tunneling components is accurately described. This global fit represents a complete description of the VRT transitions of (H2O)3 up to 150 cm−1, and complements our similar treatment of the (D2O)3 torsional dynamics.