THEORETICAL STUDY ON FERMI RESONANCE OF THE EXCESS PROTON VIBRATION IN BINARY CLUSTERS

Abstract

In protonated binary clusters, location and magnitude of delocalization of the excess proton is shown to correlate to the difference of the proton affinities of the two components\textbf{316}, 249 (2007).}. Theoretical calculations on a series of protonated binary clusters have shown that Fermi resonance can occur in clusters containing amines. For examples, in (CH${_3}$)${_3}$N-H$^{+}$-X, the N-H$^{+}$ stretching frequency is high than the first overtone of N-H$^{+}$ bending modes. As the N-H$^{+}$ stretching frequency decreases by increasing the proton affinity of X, Fermi resonance inevitably shall occur. At least both N-H$^{+}$ bending modes seem to couple with the N-H$^{+}$ stretching mode; we performed multi-dimensional mode analyses to understand this coupling.