The initial Wigner distribution is sampled from the ground vibrational state ν = 0 on the ground electronic state |S 0 , where the normal mode frequencies (in the harmonic approximation) are calculated based on the approach outlined in Refs. 74 and 75, as implemented in the SHARC package. For all molecules, the normal mode frequencies are computed at the level of MP2/6-31++G** with the MOLPRO package, with the optimized structure obtained at the same level of electronic structure theory for the ground electronic state. In particular, the nuclear density ρ W ( R, P) in terms of the molecular normal-mode frequencies {ω k } and phase space variables { R, P} is given as