Observation of intra- and intermolecular vibrational coherences of the aqueous tryptophan radical induced by photodetachment (original) (raw)
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Nature Communications
The elementary processes that accompany the interaction of ionizing radiation with biologically relevant molecules are of fundamental importance. However, the ultrafast structural rearrangement dynamics induced by the ionization of biomolecules in aqueous solution remain hitherto unknown. Here, we employ femtosecond optical pump-probe spectroscopy to elucidate the vibrational wave packet dynamics that follow the photodetachment of phenoxide, a structural mimic of tyrosine, in aqueous solution. Photodetachment of phenoxide leads to wave packet dynamics of the phenoxyl radical along 12 different vibrational modes. Eight of the modes are totally symmetric and support structural rearrangement upon electron ejection. Comparison to a previous photodetachment study of phenoxide in the gas phase reveals the important role played by the solvent environment in driving ultrafast structural reorganization induced by ionizing radiation. This work provides insight into the ultrafast molecular dynamics that follow the interaction of ionizing radiation with molecules in aqueous solution.
Femtosecond photoassociation: Coherence and implications for control in bimolecular reactions
The Journal of Chemical Physics, 1997
A theoretical analysis of the recent femtosecond photoassociation spectroscopy ͑FPAS͒ experiment on mercury ͓U. Marvet and M. Dantus, Chem. Phys. Lett. 245, 393 ͑1995͔͒ is presented. It is shown that when a thermal distribution of diatom collision pairs is excited from a free to a bound electronic state on a time scale shorter than molecular vibration, an ensemble of coherent wave packets is produced. The dynamics of these wave packets created by the photoassociation pulse can be observed by firing a second probe pulse at variable time delays, and the depletion of the first excited bound state by the probe pulse is detected via fluorescence of the remaining population. Simulations of the FPAS experiment, using both wave packet propagation techniques and perturbation theory, clearly show the vibrational dynamics of the photoassociated transients. It is also demonstrated how the FPAS technique may be used as a tool for controlling the energy, impact parameter, and orientation in bimolecular reactions.
The theory of ultrafast vibrational spectroscopy
Chemical physics, 1995
This paper discusses the use of ultrafast time-resolved IR spectroscopy to probe vibrational modes that are coupled to photochemically induced reactions. A detailed theory is derived that describes the IR probe signals in three different schemes: pulsed-pump, pulsed-probe spectroscopy in which the total power of the transmitted probe pulse is measured, pulsed-pump, pulsed-probe spectroscopy in which the probe pulse is spectrally dispersed after the sample and pulsed-pump, cw-probe with gating after the sample. It is found that the three schemes lead to subtly different signals which may greatly affect the interpretation of experiments. Also the coherent excitation of vibrational modes that are both IR and Franck-Condon active is considered. 0301-0104/95/$09.50
Femtosecond time-resolved spectroscopy of elementary molecular dynamics
Naturwissenschaften, 2002
Femtosecond time-resolved coherent anti-Stokes Raman spectroscopy (CARS) is applied in order to prepare and monitor laser-induced vibrational coherences (wave packets) of different samples mainly in its electronic ground state but also in excited states. The time evolution of these wave packets gives information on the dynamics of molecular vibrations. In a first example the femtosecond (fs) CARS transients of iodine are investigated. By changing the relative delay between the applied laser pulses of this non-degenerated four-wave mixing technique, both the wavepacket motion on the electronically excited and the ground states can be detected as oscillations in the coherent anti-Stokes signal. Second we report on selective excitation of the vibrational modes in the electronic ground state of polymers of diacetylene by means of a femtosecond time-resolved CARS scheme. This selectivity is achieved by varying the phase shape (chirp) and the relative delay between the exciting laser pulses.
Ultrafast light-induced dynamics in solvated biomolecules: The indole chromophore with water
2021
Jolijn Onvlee,1, 2, ∗ Sebastian Trippel,1, 2 and Jochen Küpper1, 2, 3, 4, † Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany Center for Ultrafast Imaging, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany Department of Physics, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany Department of Chemistry, Universität Hamburg, Martin-Luther-King-Platz 6, 20146 Hamburg, Germany (Dated: March 15, 2021)
Femtosecond Dynamics of Unimolecular and Unrestricted Bimolecular Reactions
The Journal of Physical Chemistry A, 1998
The results of two time-resolved experiments using femtosecond laser pulses are presented. In the first, molecular photoinduced detachment of I 2 from methylene iodide is studied. The progress of the reaction is monitored by selective detection of fluorescence from the iodine product; molecular dynamics are probed by depletion of the fluorescent state. Pump-probe spectroscopy of the halogen moiety following high-energy (12 eV) excitation reveals that the reaction proceeds by a concerted asynchronous mechanism. The second experiment is a real-time study of an unrestricted bimolecular reaction. In this process, gas phase mercury atoms are photoassociated to an electronically excited state using a femtosecond pulse; the real-time dynamics of the resulting excimers are probed by fluorescence depletion using a second pulse. Analysis of the rotational anisotropy in the nascent dimers reveals the degree of rotational excitation in the excited state and indicates the impact parameter selectivity of the photoassociation process.
Physical Review Letters, 2009
We present a combined theoretical and experimental study of ultrafast wave-packet dynamics in the dissociative ionization of H 2 molecules as a result of irradiation with an extreme-ultraviolet (XUV) pulse followed by an infrared (IR) pulse. In experiments where the duration of both the XUV and IR pulses are shorter than the vibrational period of H 2 þ , dephasing and rephasing of the vibrational wave packet that is formed in H 2 þ upon ionization of the neutral molecule by the XUV pulse is observed. In experiments where the duration of the IR pulse exceeds the vibrational period of H 2 þ (15 fs), a pronounced dependence of the H þ kinetic energy distribution on XUV-IR delay is observed that can be explained in terms of the adiabatic propagation of the H 2 þ wave packet on field-dressed potential energy curves.
Photo-induced protein dynamics measured by femtosecond time-resolved luminescence
Journal of Luminescence, 2003
The early stage in the photo-induced dynamics of photoactive yellow protein in aqueous solution has been investigated at room temperature by the femtosecond luminescence spectroscopy using an optical Kerr-gate technique. Remarkable oscillatory components have been directly observed with the time resolution of 180 fs and the spectral resolution of 5 nm: Mapping the phase of oscillations in time at each wavelength reveals that each oscillation is restricted in the respective narrow spectral region, the period and amplitude of which are 500-800 fs and 100-200 cm À1 ; respectively. Since the mean spectral position of each component seems to be related to the molecular vibrational energy, the oscillatory components are possibly attributed to the combination of the intramolecular vibrations of the chromophore and the surrounding protein motions. r
The Journal of Physical Chemistry A, 2005
The photodissociation dynamics of the acetone S 2 (n, 3s) Rydberg state excited at 195 nm has been studied by using femtosecond pump-probe mass-selected multiphoton ionization spectroscopy. For the first time, the temporal evolutions of the initial state, intermediates, and methyl products were simultaneously measured and analyzed for this reaction to elucidate the complex dynamics. Two mechanisms were considered: (1) the commonly accepted mechanism in which the primary dissociation occurs on the first triplet-state surface, and (2) the recently proposed mechanism in which the primary dissociation takes place on the first singlet-excitedstate surface. Our results and analyses supported the validity of the new mechanism. On the other hand, the conventional mechanism was found to be inadequate to describe the observed dynamics. The temporal evolution of methyl products arising from the secondary dissociation of hot acetyl intermediates exhibited a very complex behavior that can be ascribed to the combination of a nonuniform initial vibrational distribution and the competition between dissociation and slow intramolecular vibrational redistribution.