title: Ultrafast time-resolved pump-probe spectroscopy of PYP by a sub-8 fs pulse laser at 400 nm.
abstract: Impulsive excitation of molecular vibration is known to induce wave packets in both the ground state and excited state. Here, the ultrafast dynamics of PYP was studied by pump-probe spectroscopy using a sub-8 fs pulse laser at 400 nm. The broadband spectrum of the UV pulse allowed us to detect the pump-probe signal covering 360-440 nm. The dependence of the vibrational phase of the vibrational mode around 1155 cm(-1) on the probe photon energy was observed for the first time to our knowledge. The vibrational mode coupled to the electronic transition observed in the probe spectral ranges of 2.95-3.05 and 3.15-3.35 eV was attributed to the wave packets in the ground state and the excited state, respectively. The frequencies in the ground state and excited state were determined to be 1155 ± 1 and 1149 ± 1 cm(-1), respectively. The frequency difference is due to change after photoexcitation. This means a reduction of the bond strength associated with π-π* excitation, which is related to the molecular structure change associated with the primary isomerization process in the photocycle in PYP. Real-time vibrational modes at low frequency around 138, 179, 203, 260, and 317 cm(-1) were also observed and compared with the Raman spectrum for the assignment of the vibrational wave packet.
authors.affiliation: Advanced Ultrafast Laser Research Center, University of Electro-Communications, Chofugaoka 1-5-1, Chofu, Tokyo 182-8585 Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
authors.forename: Atsushi
authors.initials: A
authors.lastname: Yabushita
authors.forename: Seiji
authors.initials: S
authors.lastname: Taniguchi
authors.forename: Haik
authors.initials: H
authors.lastname: Chosrowjan
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Imamoto
authors.forename: Keiichi
authors.initials: K
authors.lastname: Sueda
authors.forename: Noriaki
authors.initials: N
authors.lastname: Miyanaga
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Kobayashi
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D003373:Coumaric Acids / Q000737:chemistry; D004583:Electrons; D005583:Fourier Analysis; D020607:Halorhodospira halophila / Q000378:metabolism; D007834:Lasers; D020283:Photoreceptors, Microbial / Q000737:chemistry* / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet; D013059:Spectrum Analysis, Raman; D013997:Time Factors; D014732:Vibration
chemical_list: D001426:Bacterial Proteins; D003373:Coumaric Acids; D020283:Photoreceptors, Microbial; C050162:photoactive yellow protein, Bacteria