title: Anharmonic couplings underlying the ultrafast vibrational dynamics of hydrogen bonds in liquids.
abstract: 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).
authors.affiliation: Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, 12489 Berlin, Germany.
authors.forename: N
authors.initials: N
authors.lastname: Huse
authors.forename: B D
authors.initials: BD
authors.lastname: Bruner
authors.forename: M L
authors.initials: ML
authors.lastname: Cowan
authors.forename: J
authors.initials: J
authors.lastname: Dreyer
authors.forename: E T J
authors.initials: ET
authors.lastname: Nibbering
authors.forename: R J D
authors.initials: RJ
authors.lastname: Miller
authors.forename: T
authors.initials: T
authors.lastname: Elsaesser