Journal of Physical Chemistry A, Vol.123, No.8, 1529-1537, 2019
Multidimensional H Atom Tunneling Dynamics of Phenol: Interplay between Vibrations and Tunneling
Multidimensional facets of the hydrogen tunneling dynamics of phenol excited in S-1 (pi pi*) have been unraveled to give particular S-1 vibronic states strongly coupled or actively decoupled to the O-H tunneling coordinate. Strong mode-dependent variation of the tunneling rate measured with picosecond lasers indicates that tunneling probability is extremely sensitive to low-frequency vibrational modes seemingly orthogonal to the O-H elongation coordinate unless the rate of energy randomization exceeds that of tunneling. The multidimensional nature of tunneling has also been manifested in efficient internal-to-translational energy transfers observed at S-1 vibronic modes strongly coupled to the tunneling coordinate, giving insights into otherwise the formidable multidimensional map of tunneling process. The nonadiabatic bifurcation dynamics in the later stage of the chemical reaction has been disentangled by analyzing picosecond time-resolved product state distributions, resolving a long controversial issue regarding the origin of high or low kinetic energy component of the product translational energy distributions.