Tracking ultrafast dynamics of n-propylbenzene cations by delayed photofragmentation and photoelectron spectroscopy

Liu, Yuzhu; Gerber, T.; Gai-Ge, None Zheng; Xiao, Shaorong; Cheng, Qiuming; Knopp, G.

doi:10.1016/j.jms.2016.11.009

Cited by 7 publications

(2 citation statements)

References 25 publications

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“…Among multiple time-resolved methods, time-resolved photoionization spectroscopy, which involves a pump-probe framework, has offered rich and radical dynamical information about many elementary reactions in chemistry, physics, and biology 8 – 11 . After the molecule is prepared in the superposition state by coherent excitation of the eigenstates of interest with an initial laser pulse, the time-dependent vibrational motion is followed by monitoring either the parent-ion signal or the photoelectron kinetic energy (PKE) distribution 12 – 17 as a function of the pump-probe delay time. If the probing transition is sensitive to the changes in interatomic distance, i.e., the time evolution of the vibrational wave packet, the measured signal will provide direct ‘snapshots’ of the molecular motions.…”

Section: Introductionmentioning

confidence: 99%

Femtosecond time-resolved observation of butterfly vibration in electronically excited o-fluorophenol

Ling

Song

et al. 2017

Sci Rep

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The butterfly vibration during the hydrogen tunneling process in electronically excited o-fluorophenol has been visualized in real time by femtosecond time-resolved ion yield spectroscopy coupled with time-resolved photoelectron imaging technique. A coherent superposition of out-of-plane C–F butterfly motions is prepared in the first excited electronic state (S1). As the C–F bond vibrates with respect to the aromatic ring, the nuclear geometry varies periodically, leading to the corresponding variation in the photoionization channel. By virtue of the more favorable ionization probability from the nonplanar minimum via resonance with the Rydberg states, the evolution of the vibrational wave packet is manifested as a superimposed beat in the parent-ion transient. Moreover, time-resolved photoelectron spectra offer a direct mapping of the oscillating butterfly vibration between the planar geometry and nonplanar minimum. The beats for the photoelectron peaks originating from the planar geometry are out of phase with those from the nonplanar minimum. Our results provide a physically intuitive and complete picture of the oscillatory flow of energy responsible for the coherent vibrational motion on the excited state surface.

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Section: Introductionmentioning

confidence: 99%

Femtosecond time-resolved observation of butterfly vibration in electronically excited o-fluorophenol

Ling

Song

et al. 2017

Sci Rep

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“…Therefore, time-dependent ion depletion signal measured at probe wavelengths near 400 nm is expected to reveal the ionic PT dynamics. Similar pump–probe detection schemes have been employed by other groups to investigate ultrafast dynamics in a variety of ionic systems. − Our approach is also similar in concept to the picosecond time-resolved UV-ionization/IR-dip spectroscopy that has been used to study photoionization-induced rearrangement dynamics of nonpolar solvents − and water − in aromatic complex cations. Although IR probing provides very detailed spectroscopic information, it is probably not applicable to very strongly bound ionic complexes (>1 eV) such as the one discussed here.…”

Section: Introductionmentioning

confidence: 97%

Ultrafast Protonation of an Amide: Photoionization-Induced Proton Transfer in Phenol-Dimethylformamide Complex Cation

Cheng

2019

J. Phys. Chem. A

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In this study we explore the photoionization-induced proton transfer (PT) dynamics in the hydrogen-bonded complex of phenol (PhOH) and a simple amide, dimethylformamide (DMF). Neutral PhOH-DMF complexes produced in a supersonic expansion are photoionized by femtosecond 1 + 1 resonance-enhanced multiphoton ionization via its S1 state, and the subsequent PT dynamics occurring in the [PhOH-DMF]+ cation is probed by delayed pulses that lead to ion fragmentation. The experiments and density functional theory calculations reveal that the photoionization-induced PT proceeds in two consecutive steps of very different time scales. Upon femtosecond ionization the [PhOH-DMF]+ cation is initially prepared with a non-PT geometry close to that of the dominant neutral complex. The ionic system then rapidly relaxes into a configuration possessing both non-PT and PT characteristics in ∼0.5 ps. This partial-PT intermediate then undergoes a much slower barrier crossing in ∼25 ps to a more stable structure in which PT is more complete. The slow isomerization step not only corresponds to PT but also to a hydrogen-bonding site switching. The present study simulates a scenario of suddenly bringing a strong acid to the close vicinity of an amide to watch how protonation occurs. Our results suggest that the initial protonation of a peptide-like unit in acid-induced protein processes requires a relaxation time of ∼0.5 ps, which must be taken into account in complete descriptions of protein dynamics.

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Real-time observation of cascaded electronic relaxation processes in p-Fluorotoluene

Hao

Deng

Long

et al. 2017

Spectrochimica Acta Part A: Molecular and Biomolecular Spectros

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Tracking ultrafast dynamics of n-propylbenzene cations by delayed photofragmentation and photoelectron spectroscopy

Cited by 7 publications

References 25 publications

Femtosecond time-resolved observation of butterfly vibration in electronically excited o-fluorophenol

Femtosecond time-resolved observation of butterfly vibration in electronically excited o-fluorophenol

Ultrafast Protonation of an Amide: Photoionization-Induced Proton Transfer in Phenol-Dimethylformamide Complex Cation

Real-time observation of cascaded electronic relaxation processes in p-Fluorotoluene

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