Marcus Motzkus

Universität Heidelberg, Heidelberg, Baden-Wuerttemberg, Germany

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Publications (152)360.14 Total impact

  • Tiago Buckup, Marcus Motzkus
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    ABSTRACT: Multidimensional femtosecond time-resolved vibrational coherence spectroscopy allows one to investigate the evolution of vibrational coherence in electronic excited states. Methods such as pump-degenerate four-wave mixing and pump-impulsive vibrational spectroscopy combine an initial ultrashort laser pulse with a nonlinear probing sequence to reinduce vibrational coherence exclusively in the excited states. By carefully exploiting specific electronic resonances, one can detect vibrational coherence from 0 cm(-1) to over 2,000 cm(-1) and map its evolution. This review focuses on the observation and mapping of high-frequency vibrational coherence for all-trans biological polyenes such as β-carotene, lycopene, retinal, and retinal Schiff base. We discuss the role of molecular symmetry in vibrational coherence activity in the S1 electronic state and the interplay of coupling between electronic states and vibrational coherence. Expected final online publication date for the Annual Review of Physical Chemistry Volume 65 is March 31, 2014. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.
    Annual Review of Physical Chemistry 11/2013; · 13.37 Impact Factor
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    ABSTRACT: In the present work we have explored the ultrafast relaxation network of coumarin and umbelliferone (7-hydroxy-coumarin) using time-resolved femtosecond spectroscopy and quantum chemical calculations. Despite the importance of the photophysical properties of coumarin derivatives for applications in biomedicine, the low fluorescence quantum yield of coumarin itself has not been fully understood so far. On the basis of our combined experimental and theoretical results we suggest a model for the ultrafast decay after photoexcitation incorporating two parallel radiationless relaxation pathways: one within the initially excited state via ring opening and the other one by transition into a dark state along the carbonyl stretching mode. The fluorescence quantum yield is determined by the position of the branching point relative to the Franck-Condon region which is strongly influenced by interactions with the environment and the substitution pattern. This model is finally capable of giving a comprehensive account of the striking differences observed in the photophysical behavior of coumarin as opposed to umbelliferone.
    Physical Chemistry Chemical Physics 09/2013; · 3.83 Impact Factor
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    ABSTRACT: Detection of short-lived transient species is a major challenge in femtosecond spectroscopy, especially when third-order techniques like transient absorption are used. Higher order methods employ additional interactions between light and matter to highlight such transient species. In this work we address numerically and experimentally the detection of ultrafast species with pump-Degenerate Four Wave Mixing (pump-DFWM). In this respect, conclusive identification of ultrafast species requires the proper determination of time-zero between all four laser pulses (pump pulse and the DFWM sequence). This is addressed here under the light of experimental parameters as well as molecular properties: The role of pulse durations, amount of pulse chirp as well as excited state life time is investigated by measuring a row of natural pigments differing mainly in the number of conjugated double bonds (N = 9 to 13). A comparison of the different signals reveals a strikingly unusual behavior of spheroidene (N = 10). Complete analysis of the pump-DFWM signal illustrates the power of the method and clearly assigns the uniqueness of spheroidene to a mixing of the initially excited state with a dark excited electronic state.
    The Journal of Chemical Physics 08/2013; 139(7):074202. · 3.12 Impact Factor
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    ABSTRACT: Pump-impulsive vibrational spectroscopy (pump-IVS) is used to record excited state vibrational dynamics following photoexcitation of two carotenoids, β-carotene and lycopene, with <30 fs temporal resolution, and covering the full vibrational spectrum of the investigated chromophores. The results record the course of S2-S1 internal conversion, followed by vibrational relaxation and decay to the electronic ground state. This interpretation is corroborated by comparison with pump-degenerate-four-wave-mixing (pump-DFWM) experiments on the same systems. The results demonstrate the potential of both time-domain spectroscopic techniques to resolve photochemical dynamics, including fingerprint frequencies which directly reflect changes in bonding and structure in the nascent sample. The exclusive strengths and limitations of these two methods are compared with those presented by the frequency-domain Femtosecond Stimulated Raman Scattering (FSRS) technique, highlighting the complementary nature of the three, and the benefits of using them in concert to investigate vibrational dynamics in reactive species.
    Physical Chemistry Chemical Physics 07/2013; · 3.83 Impact Factor
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    ABSTRACT: Chemical and structural composition of wood biomass is studied by label-free and chemically specific Coherent Anti-Stokes Raman Scattering (CARS) microscopy. A concept developed for assignment and semi-quantitative imaging of sample components; cellulose, hemicellulose, and lignin; by multiplex CARS microspectroscopy and subsequent data analysis is presented. Specific imaging without fluorescence backround is achieved an order of magnitude faster compared with conventional Raman microscopy. Laser polarization control yield information on molecular arrangement in wood fibers. Narrowband CARS excitation of single vibrations allows for three-dimensional volume imaging. Thus, CARS microscopy has potential as an important instrument for characterization of lignocellulosic materials. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim).
    Journal of Biophotonics 07/2013; · 3.10 Impact Factor
  • International Quantum Electronics Conference; 05/2013
  • The European Conference on Lasers and Electro-Optics; 05/2013
  • The European Conference on Lasers and Electro-Optics; 05/2013
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    ABSTRACT: Using phase-shaped millijoule 1030-nm femtosecond pulses generating a filament in a cell filled with N2, we obtain intense forward UV emission between vibrational manifolds of B2Σ and X2Σ states of N2+ for optimal pulse sequences. The effect is tentatively ascribed to wave-mixing between intense NIR pulses and weak supercontinuum components, resonant to the UV transitions, whereby a non-instantaneous nonlinear susceptibility is linked to rotational coherence in ions.
    03/2013;
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    ABSTRACT: The coupling between molecular vibrational modes in the excited state is investigated by resonant Raman two-dimensional time resolved spectroscopy. Resonant 2D Raman exploits electronic resonances to enhance fifth-order signals. We apply this approach to several (bio-)chromophores in solution.
    03/2013;
  • J. P. Kraack, T. Buckup, M. Motzkus
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    ABSTRACT: Resonant two-photon excitation is observed in Bacteriorhodopsin using transient absorption experiments with hyperspectral probing (440 - 770 nm) at different excitation wavelengths. Signal contributions from ground as well as excited electronic states show distinct dependences on excitation energies and wavelengths during all timescales of population relaxation. An additional photoproduct is observed upon high-energy excitation with an absorption maximum red-shifted with respect to the known K-intermediate, exclusively formed under linear excitation conditions. Spectral signatures of this photoproduct persist on a timescale of tens of nanoseconds after excitation, comparable to the lifetime of the K-intermediate. The observed additional photoproduct is likely to be a precursor state of an eventually forming blue-shifted, thermally stable photoproduct observed under prolonged high-intensity illumination of BR samples.
    03/2013;
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    ABSTRACT: Mapping of defects in bulk samples of single-walled carbon nanotubes (SWNT) is performed via multiplex coherent anti-Stokes Raman microscopy. The D and G vibrational bands are acquired simultaneously and their relative amplitude is used as a criterion to quantify the local purity in spin-coated SWNT samples. We observe that defects induced by oxidation are related to the spatial dispersion of nanotubes in a solid distribution.
    Nano Letters 01/2013; · 13.03 Impact Factor
  • Jan Philip Kraack, Tiago Buckup, Marcus Motzkus
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    ABSTRACT: Coherent vibrational dynamics of retinal in excited electronic states are of primary importance in the understanding of photobiology. Using pump-DFWM, we demonstrate for the first time the existence of coherent double-bond high-frequency modulations (>1300 cm–1) in the excited electronic state of different retinal derivatives. All-trans retinal as well as retinal Schiff bases exhibit a partial frequency downshift of the C═C double-bond mode from 1580 cm–1 in the ground state to 1510 cm–1 in the excited state. In addition, a new vibrational band at 1700 cm–1 assigned to the C═N stretching mode in retinal Schiff bases in the excited state is detected. The newly reported bands are observed only in specific spectral regions of excited-state absorption. Implications regarding the observation of vibrational coherences in naturally occurring retinal protonated Schiff bases in rhodopsins are discussed.
    Journal of Physical Chemistry Letters 01/2013; 4(3):383–387. · 6.59 Impact Factor
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    ABSTRACT: In this report, we demonstrate how to obtain Raman spectra from single‐beam CARS measurements under the condition of strong overlapping two‐photon excited fluorescence (2PEF). Our approach is based on the use of a narrowband phase gate implemented via femtosecond laser pulse shaping from a single broadband laser source, without any use of polarization or amplitude modulation. The decisive quantity regarding the creation of 2PEF with shaped laser pulses is the second harmonic power spectrum, which shows a different dependence on the excitation phase from the CARS signal generation. By shifting the phase or the position of the gate in an appropriate way, it is possible to keep the second harmonic power spectrum and 2PEF constant, paving the way for an elimination of it. This allows to reconstruct the Raman signal and to retrieve quantitative information of resonances even when the fluorescence is about 160 times larger than the CARS signal. Copyright © 2013 John Wiley & Sons, Ltd.
    Journal of Raman Spectroscopy 01/2013; 44(10). · 2.68 Impact Factor
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    ABSTRACT: A method for the full determination of the third-order nonlinear coherent anti-Stokes Raman scattering (CARS) susceptibility is presented, which relies on phase control of a single ultrabroadband femtosecond laser pulse. A narrowband phase gate is scanned to perform double quadrature spectral interferometry, which reveals amplitude and phase of a multiplex CARS field. A single calibration measurement in a nonresonant sample allows for the characterization of the susceptibility in amplitude and phase. This scheme is demonstrated experimentally for the fingerprint region of toluene.
    Optics Letters 10/2012; 37(20):4239-41. · 3.39 Impact Factor
  • Jan Philip Kraack, Tiago Buckup, Marcus Motzkus
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    ABSTRACT: We apply spectrally-resolved pump degenerate four-wave-mixing for the characterization of excited state low-frequency vibrational coherences during the initial events in excited state double-bond isomerization of retinal protonated Schiff-bases. A set of low-frequency coherences in the energetic range of 100-350 cm(-1) appears in the dynamics already for very early delays after initial excitation (<100 fs). The modulations are rapidly damped (<800 fs) and detectable only in a certain time window after initial excitation (<0.6 ps). Following the initial relaxation process, which leads the molecule to a stationary point in the S(1) state, it is not possible to re-excite the coherences in the excited state. Based on our observations, we conclude that the activation of the coherences is only possible to occur in a well-defined region of the excited state potential near the Franck-Condon region. Our results give direct experimental indication for the validity of the "Two-State-Two-Mode model", frequently applied for the interpretation of retinal isomerization dynamics.
    Physical Chemistry Chemical Physics 09/2012; 14(40):13979-88. · 3.83 Impact Factor
  • Alexander Wipfler, Tiago Buckup, Marcus Motzkus
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    ABSTRACT: Multiplex detection of single beam coherent anti-Stokes Raman spectra is achieved by phase shaping of a narrow gate probe. The spectrally resolved signal is amplified via a local oscillator derived from the same single beam and is disentangled via double quadrature spectral interferometry. Spectral resolution and spectral range are defined by the width and position of the phase gate, which can be easily set by a femtosecond pulse shaper. Such phase-only multiplexed single beam coherent anti-Stokes Raman spectroscopy is demonstrated for simple molecules and is combined with Raman line reconstruction methods to obtain dispersion free Raman resonances.
    Applied Physics Letters 02/2012; 100(7). · 3.79 Impact Factor
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    ABSTRACT: We report on experimental results in adaptive control over UV fluorescence from a femtosecond filament created in nitrogen. We demonstrate that an optimized sequence of femtosecond pulses can effectively align, selectively ionize and excite molecular nitrogen ions, resulting in stimulated amplification of a filament continuum seeded emission at 391 nm, 358 nm and 428 nm wavelengths.
    Lasers and Electro-Optics (CLEO), 2012 Conference on; 01/2012
  • J. Möhring, T. Buckup, M. Motzkus
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    ABSTRACT: A quantum control spectroscopy (QCS) approach using directly shaped UV excitation pulse is demonstrated. Ultrafast tailored pulses in the region of 310–335 nm are combined with transient absorption to investigate reactive pathways in the excited state of (2,2′-bipyridyl)-3,3′-diol BP(OH) $_2$. In particular, we apply QCS in the disentanglement of the competing excited-state intramolecular proton-transfer (ESIPT) channels of BP(OH)$_2$. Our results challenge parallel reactive pathways in the excited state and suggest a newer model based on an extremely fast sequential double ESIPT process.
    IEEE Journal of Selected Topics in Quantum Electronics 01/2012; 18(1):449-459. · 4.08 Impact Factor
  • Jan Philip Kraack, Tiago Buckup, Marcus Motzkus
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    ABSTRACT: We report on vibrational coherence dynamics in excited and ground electronic states of all-trans retinal protonated Schiff-bases (RPSB), investigated by time-resolved Degenerate Four-Wave-Mixing (DFWM). The results show that wave packet dynamics in the excited state of RPSB consist of only low-frequency (<800 cm(-1)) modes. Such low-frequency wave packet motion is observed over a broad range of detection wavelengths ranging from excited state absorption (∼500 nm) to stimulated emission (>600 nm). Our results indicate that low-frequency coherences in the excited state are not activated directly by laser excitation but rather by internal vibrational energy redistribution. This is supported by the observation that similar coherence dynamics are not observed in the electronic ground state. Challenging previous experimental results, we show that the formation of low-frequency coherence dynamics in RPSB does not require significant excess vibrational energy deposition in the excited state vibrational manifolds. Concerning ground state wave packet dynamics, we observe a set of high-frequency (>800 cm(-1)) modes, reflecting mainly single and double bond stretching motion in the retinal polyene-chain. Dephasing of these high-frequency coherences is mode-dependent and partially differs from analogous vibrational dephasing of the all-trans retinal chromophore in a protein environment (bacteriorhodopsin).
    Physical Chemistry Chemical Physics 12/2011; 13(48):21402-10. · 3.83 Impact Factor

Publication Stats

2k Citations
360.14 Total Impact Points

Institutions

  • 2009–2012
    • Universität Heidelberg
      • Institute of Physical Chemistry
      Heidelberg, Baden-Wuerttemberg, Germany
    • Universiteit Twente
      • Institute for Nanotechnology (MESA+)
      Enschede, Provincie Overijssel, Netherlands
  • 190–2010
    • Philipps-Universität Marburg
      • • Fachgebiet Physikalische Chemie
      • • Faculty of Chemistry
      Marburg an der Lahn, Hesse, Germany
  • 2008
    • FOM Institute AMOLF
      Amsterdamo, North Holland, Netherlands
  • 1993–2005
    • Max Planck Institute of Quantum Optics
      Arching, Bavaria, Germany
  • 2004
    • National Institute of Standards and Technology
      Maryland, United States
    • Massachusetts Institute of Technology
      Cambridge, Massachusetts, United States
  • 2002
    • Lund University
      • Department of Physical Chemistry
      Lund, Skane, Sweden
  • 2001
    • Paul Scherrer Institut
      Aargau, Switzerland
  • 1995
    • Karl-Franzens-Universität Graz
      Gratz, Styria, Austria
  • 1992
    • Universidade Federal do Rio Grande do Sul
      Pôrto de São Francisco dos Casaes, Rio Grande do Sul, Brazil