Ultraviolet transient absorption, transient grating and photon echo studies of aqueous tryptophan

Ajdarzadeh, Ahmad; Consani, Cristina; Bräm, Olivier; Tortschanoff, A.; Cannizzo, Andrea; Chergui, Majed

doi:10.1016/j.chemphys.2013.01.036

Cited by 10 publications

(10 citation statements)

References 62 publications

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“…The advent of ultrafast spectroscopy some 25 years ago triggered a real revolution in molecular photochemistry and photophysics due to its ability to probe phenomena on the time scale of molecular vibrations . In the study of condensed phase systems (molecules in solution, proteins, materials), an impressive variety of experimental methodologies has been used and developed, such as pump–probe transient absorption spectroscopy in the visible to the infrared spectral ranges, , fluorescence up-conversion, , nonlinear optical techniques (photon echo, transient grating), , and more recently multidimensional spectroscopies. − Many of these have been extended to other spectral ranges, such as the UV for nonlinear , and multidimensional spectroscopies, , the extreme UV (EUV) for photoelectron spectroscopy (UPS) of liquid samples, , or the soft and hard X-ray regions for transient X-ray absorption spectroscopy (XAS) − or X-ray emission spectroscopy (XES). − In combination with advanced computational methods, ,− these tools have delivered an unsurpassed insight into the ultrafast photoinduced dynamics of molecular systems.…”

Section: Introductionmentioning

confidence: 99%

Ultrafast Photophysics of Transition Metal Complexes

2015

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The properties of transition metal complexes are interesting not only for their potential applications in solar energy conversion, OLEDs, molecular electronics, biology, photochemistry, etc. but also for their fascinating photophysical properties that call for a rethinking of fundamental concepts. With the advent of ultrafast spectroscopy over 25 years ago and, more particularly, with improvements in the past 10-15 years, a new area of study was opened that has led to insightful observations of the intramolecular relaxation processes such as internal conversion (IC), intersystem crossing (ISC), and intramolecular vibrational redistribution (IVR). Indeed, ultrafast optical spectroscopic tools, such as fluorescence up-conversion, show that in many cases, intramolecular relaxation processes can be extremely fast and even shorter than time scales of vibrations. In addition, more and more examples are appearing showing that ultrafast ISC rates do not scale with the magnitude of the metal spin-orbit coupling constant, that is, that there is no heavy-atom effect on ultrafast time scales. It appears that the structural dynamics of the system and the density of states play a crucial role therein. While optical spectroscopy delivers an insightful picture of electronic relaxation processes involving valence orbitals, the photophysics of metal complexes involves excitations that may be centered on the metal (called metal-centered or MC) or the ligand (called ligand-centered or LC) or involve a transition from one to the other or vice versa (called MLCT or LMCT). These excitations call for an element-specific probe of the photophysics, which is achieved by X-ray absorption spectroscopy. In this case, transitions from core orbitals to valence orbitals or higher allow probing the electronic structure changes induced by the optical excitation of the valence orbitals, while also delivering information about the geometrical rearrangement of the neighbor atoms around the atom of interest. With the emergence of new instruments such as X-ray free electron lasers (XFELs), it is now possible to perform ultrafast laser pump/X-ray emission probe experiments. In this case, one probes the density of occupied states. These core-level spectroscopies and other emerging ones, such as photoelectron spectroscopy of solutions, are delivering a hitherto unseen degree of detail into the photophysics of metal-based molecular complexes. In this Account, we will give examples of applications of the various methods listed above to address specific photophysical processes.

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Section: Introductionmentioning

confidence: 99%

Ultrafast Photophysics of Transition Metal Complexes

2015

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“…Three-pulse photon-echo peak shift (3PEPS) measurements revealed a solvent independent coherent response for times <0.1 ps, described as inertial, followed by a solvent dependent component changing from 4.04 ps to 1.36 ps in ethylene glycol at 297 K and 397 K . Fluorescence upconversion measurements with broad-band detection also can yield insights into the intra- and intermolecular dynamics that are comparable to those for other nonlinear optical techniques. , Our goal is to find spectroscopic probes of the solvation environment that are sensitive and easier to implement in a microscope; in particular, we evaluate here chirped femtosecond pulses. These single-beam methods will be of paramount importance when investigating microenvironment effects on single molecules due to the relative ease of the experimental implementation.…”

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Solvent Environment Revealed by Positively Chirped Pulses

Konar

Lozovoy

Dantus

2014

J. Phys. Chem. Lett.

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The spectroscopy of large organic molecules and biomolecules in solution has been investigated using various time-resolved and frequency-resolved techniques. Of particular interest is the early response of the molecule and the solvent, which is difficult to study due to the ambiguity in assigning and differentiating inter- and intramolecular contributions to the electronic and vibrational populations and coherence. Our measurements compare the yield of fluorescence and stimulated emission for two laser dyes IR144 and IR125 as a function of chirp. While negatively chirped pulses are insensitive to solvent viscosity, positively chirped pulses are found to be uniquely sensitive probes of solvent viscosity. The fluorescence maximum for IR125 is observed near transform-limited pulses; however, for IR144, it is observed for positively chirped pulses once the pulses have been stretched to hundreds of femtoseconds. We conclude that chirped pulse spectroscopy is a simple one-beam method that is sensitive to early solvation dynamics.

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“…Pioneering non-heterodyne detected 3PPE experiments in the UV region were performed by the Chergui group on dye molecules 61,62 and tryptophan. 63 Moran and coworkers 64,65 employed the 3PPE geometry, using diffraction gratings for the generation of non-collinear phase-locked UV pulse pairs in a boxcar geometry and fused silica wedges for delay control. UV pulses with an z900 cm À1 bandwidth were generated by four-wave-mixing, in an argon-lled hollow-core ber, of the fundamental wavelength and the second harmonic of a Ti:sapphire laser; the pulses were compressed to z25 fs by a fused silica prism pair.…”

Section: Experimental Congurations Of 2d Spectroscopymentioning

confidence: 99%