title: Vibrational relaxation pathways of amide I and amide II modes in N-methylacetamide.
abstract: We studied the vibrational energy relaxation mechanisms of the amide I and amide II modes of N-methylacetamide (NMA) monomers dissolved in bromoform using polarization-resolved femtosecond two-color vibrational spectroscopy. The results show that the excited amide I vibration transfers its excitation energy to the amide II vibration with a time constant of 8.3 ± 1 ps. In addition to this energy exchange process, we observe that the excited amide I and amide II vibrations both relax to a final thermal state. For the amide I mode this latter process dominates the vibrational relaxation of this mode. We find that the vibrational relaxation of the amide I mode depends on frequency which can be well explained from the presence of two subbands with different vibrational lifetimes (~1.1 ps on the low frequency side and ~2.7 ps on the high frequency side) in the amide I absorption spectrum.
authors.affiliation: FOM Institute AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands. l.piatkowski@amolf.nl
authors.forename: L
authors.initials: L
authors.lastname: Piatkowski
authors.forename: H J
authors.initials: HJ
authors.lastname: Bakker
mesh_terms: D000577:Amides / Q000737:chemistry*; D014732:Vibration
chemical_list: D000577:Amides