Coherent Motion of Low
Frequency Vibrations in Ultrafast
Excited State Proton Transfer
M. Pfeiffer,1C. Chudoba,1A. Lau,1K. Lenz,1and T. Elsaesser1
Received11 Apr 1997
Abstract
Photoexcitation of internal proton transfer in the tinuvin molecule causes the excitation
of some low frequency vibrational modes which oscillate with high amplitudes in a
coherent manner over 700 fs. Such effect is observed for the first time applying two color
pump/probe measurement with 25 fs pulses. Based on resonance Raman spectra a
normal coordinate analysis of the modes is performed. It is shown that the nuclear
movement given by the normal vibration of one of the modes serves to open up a
barrierfree proton transfer path.