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. (C) 1999 American Institute of Physics. [S0021-9606(99)00341-4].