Vibrational relaxation in simulated two-dimensional infrared spectra of two amide modes in solution

Arend G. Dijkstra*, Thomas la Cour Jansen, Robbert Bloem, Jasper Knoester

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

20 Citations (Scopus)
276 Downloads (Pure)

Abstract

Two-dimensional infrared spectroscopy is capable of following the transfer of vibrational energy between modes in real time. We develop a method to include vibrational relaxation in simulations of two-dimensional infrared spectra at finite temperature. The method takes into account the correlated fluctuations that occur in the frequencies of the vibrational states and in the coupling between them as a result of interaction with the environment. The fluctuations influence the two-dimensional infrared line shape and cause vibrational relaxation during the waiting time, which is included using second-order perturbation theory. The method is demonstrated by applying it to the amide-I and amide-II modes in N-methylacetamide in heavy water. Stochastic information on the fluctuations is obtained from a molecular dynamics trajectory, which is converted to time dependent frequencies and couplings with a map from a density functional calculation. Solvent dynamics with the same frequency as the energy gap between the two amide modes lead to efficient relaxation between amide-I and amide-II on a 560 fs time scale. We show that the cross peak intensity in the two-dimensional infrared spectrum provides a good measure for the vibrational relaxation. (c) 2007 American Institute of Physics.

Original languageEnglish
Article number194505
Number of pages12
JournalJournal of Chemical Physics
Volume127
Issue number19
DOIs
Publication statusPublished - 21-Nov-2007

Keywords

  • N-METHYLACETAMIDE
  • MOLECULAR-STRUCTURE
  • IR-SPECTROSCOPY
  • PHOTON-ECHO
  • DYNAMICS
  • WATER
  • PEPTIDES
  • BAND
  • SIGNATURES
  • BOND

Cite this