However, the a1-a3 actions for the H2O(v1,v2,v3) product are not directly obtained from QCT calculations. These actions were calculated using the NMA method, the normal mode analysis method, previously developed by our research group. These water actions correspond to symmetric stretching (ν1 = 3839 cm -1 ), bending (ν2 = 1603 cm -1 ) and antisymmetric stretching (ν3 = 3896 cm -1 ) modes. Note that these actions are real numbers and they are rounded to their nearest integer, n1-n3, using the standard binning approach, where each trajectory contributes with weight unity. Other more sophisticated alternatives, Gaussian binning, have been proposed to solve this problem, but in polyatomic systems we found that it does not substantially alter these populations.