Two-dimensional model treatment of torsional motions in the water trimer

Recently, three far-infrared vibrational excitations were observed for (D2O)3 in the range 40–100 cm−1 at very high resolution. These vibrations could be identified with pseudorotations (due to flipping of free OH bonds). However, a one-dimensional model to describe the pseudorotation has thus far failed to conclusively assign the measured bands to pseudorotational transitions. A coupled two-dimensional model treatment of torsional motions in the water trimer is presented. Based on the computed torsional frequencies and transition moments, new assignments of the observed vibration-rotation-tunneling spectra are proposed.