Anharmonic couplings underlying the ultrafast vibrational dynamics of hydrogen bonds in liquids.
The multilevel structure and vibrational couplings of O-H stretching transitions in intermolecular hydrogen bonds of acetic acid dimers are determined by femtosecond two-dimensional photon-echo spectroscopy in the infrared. Combining experiment and theoretical calculations, we separate Fermi resonances with combination tones of fingerprint modes from anharmonic couplings to underdamped low-frequency modes of the dimer. A multilevel density matrix approach based on density functional theory calculations reproduces the experimental results and reveals coupling strengths of both mechanisms on the order of 40-150 cm(-1).
Huse
N
N
Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, 12489 Berlin, Germany.
Bruner
B D
BD
Cowan
M L
ML
Dreyer
J
J
Nibbering
E T J
ET
Miller
R J D
RJ
Elsaesser
T
T