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Gotard Burdzinski - One of the best experts on this subject based on the ideXlab platform.

  • Time Resolved Spectroscopy of the singlet excited state of betanin in aqueous and alcoholic solutions
    Physical Chemistry Chemical Physics, 2015
    Co-Authors: Monika Wendel, Stanislaw Nizinski, Dorota Tuwalska, Karolina Starzak, Dominika Szot, Dorota Prukala, Marek Sikorski, Slawomir Wybraniec, Gotard Burdzinski
    Abstract:

    The photophysical properties of betanin in aqueous and alcoholic solutions were determined at room temperature using ultrafast UV-vis-NIR transient absorption Spectroscopy (λexc = 535 nm). Its S1 → Sn (n > 1) absorption bands appear with maxima at about λ ∼ 450 and 1220 nm. The short betanin S1 state lifeTime (6.4 ps in water) is mainly determined by the efficient S1 → S0 radiationless relaxation, probably requiring a strong change in geometry, since the S1 lifeTime grows to 27 ps in the more viscous ethylene glycol. The fluorescence quantum yield is very low (Φf ∼ 0.0007 in water), therefore this deactivation path is of minor importance. Other processes, such as S1 → T1 intersystem crossing or photoproduct formation, are virtually absent, since full S0 ← S1 ground state recovery is observed within tens of picoseconds after photoexcitation. The observed fast light-to-heat conversion in the absence of triplet excited state formation supports the idea that betanin is a photoprotector in vivo.

  • photochemical formation of thiirene and thioketene in 1 2 3 thiadiazoles with phenyl substituents studied by Time Resolved Spectroscopy
    Photochemical and Photobiological Sciences, 2013
    Co-Authors: Gotard Burdzinski, Stephanie Delbaere, Michel Sliwa, Tomasz Pedzinski, Yunlong Zhang, Julien Rehault
    Abstract:

    Photochemistry of 4-phenyl-1,2,3-thiadiazole (PT) and 4,5-diphenyl-1,2,3-thiadiazole (DPT) in solution was studied at room temperature using UV-vis and IR transient absorption spectroscopies (λex = 266 nm). Ultrafast techniques show a very fast rise (<0.3 ps) of thiirene and thioketene species, formed from 1,2,3-thiadiazoles in the singlet excited state. The remarkable unimolecular stability of thiirenes in solution is observed. On a millisecond Time scale thiirenes with phenyl substituents undergo an intermolecular reaction (dimerization of thiirene–thioketene complexes) leading to 1,3-dithiole derivatives.

  • Photochemical formation of thiirene and thioketene in 1,2,3-thiadiazoles with phenyl substituents studied by Time-Resolved Spectroscopy
    Photochemical and Photobiological Sciences, 2013
    Co-Authors: Gotard Burdzinski, Stephanie Delbaere, Michel Sliwa, Tomasz Pedzinski, Yunlong Zhang, Julien Rehault
    Abstract:

    Photochemistry of 4-phenyl-1,2,3-thiadiazole (PT) and 4,5-diphenyl-1,2,3-thiadiazole (DPT) in solution was studied at room temperature using UV-vis and IR transient absorption spectroscopies (λex = 266 nm). Ultrafast techniques show a very fast rise (

Julien Rehault - One of the best experts on this subject based on the ideXlab platform.

Mark A Berg - One of the best experts on this subject based on the ideXlab platform.

  • hilbert space treatment of incoherent Time Resolved Spectroscopy i formalism a tensorial classification of high order orientational gratings and generalized muppets echoes
    Journal of Chemical Physics, 2010
    Co-Authors: Mark A Berg
    Abstract:

    Time-Resolved Spectroscopy that uses more than one incoherent excitation, and thus has multiple periods of Time evolution, is becoming more common. A recent example is multiple population-period transient Spectroscopy (MUPPETS), which is implemented as a high-order transient grating. In this paper, a formalism is developed to treat these types of incoherent Spectroscopy in a manner that parallels the Liouville-pathway formalism used to treat multidimensional coherent Spectroscopy. A Hilbert space of incoherent (population) states is defined and general expressions for transition and Time-evolution operators acting on these states are derived from the corresponding quantum operators. This formalism describes incoherent experiments that involve an arbitrary number of temporal dimensions in terms of pathways through the Hilbert space. Each pathway is associated with a multiple-Time rate-correlation function. Previous work has shown that these multiple-Time correlation functions can measure heterogeneity in electronic-relaxation rates. Thus, they are an analog of coherent “echo” experiments, which measure heterogeneity in frequencies. We show that similar “MUPPETS echo” experiments can be done on any incoherent variable. For a dilute molecular solute, the Hilbert-space method leads to a systematic treatment of multidimensional transient gratings. The extension of irreducible-tensor methods to the incoherent Hilbert space results in a classification of orientational gratings of arbitrary order. The general methods developed in this paper are applied more specifically to single-photon, dipole transitions in the following paper.

  • hilbert space treatment of incoherent Time Resolved Spectroscopy ii pathway description of optical multiple population period transient Spectroscopy
    Journal of Chemical Physics, 2010
    Co-Authors: Mark A Berg
    Abstract:

    This paper applies the general methods developed in the previous paper (Paper I) to the case of one-photon, dipole transitions of a molecular solute. The results generalize transient-grating Spectroscopy to an arbitrarily number of dimensions. Transition and detection operators are derived, and their matrix elements are calculated in the complex-valued basis set developed in Paper I. Selection rules make it possible to analyze which incoherent pathways, and thus which correlation functions, contribute to an N-dimensional multiple population-period transient Spectroscopy experiment. Irreducible-tensor methods allow the amplitudes of the contributing orientational-correlation functions to be calculated for arbitrary polarization conditions. A second-rank polarization tensor is used to describe the polarization of the pair of beams creating or detecting a grating. Several known results for one-dimensional experiments are rederived in this formalism to provide examples of its use.

Andrius Baltuska - One of the best experts on this subject based on the ideXlab platform.

  • white light generation over three octaves by femtosecond filament at 3 9 µm in argon
    Optics Letters, 2012
    Co-Authors: Daniil Kartashov, P Bejot, Jerome Kasparian, Jeanpierre Wolf, S Alisauskas, A Pugžlys, A Voronin, A M Zheltikov, M Petrarca, Andrius Baltuska
    Abstract:

    We report the first (to our knowledge) experimental results and numerical simulations on mid-IR femtosecond pulse filamentation in argon using 0.1 TW peak-power, 80 fs, 3.9 μm pulses. A broadband supercontinuum spanning the spectral range from 350 nm to 5 μm is generated, whereby about 4% of the mid-IR pulse energy is converted into the 350-1700 nm spectral region. These mid-IR-visible coherent continua offer a new, unique tool for Time-Resolved Spectroscopy based on a mid-IR filamentation laser source.

  • scalable yb mopa driven carrier envelope phase stable few cycle parametric amplifier at 1 5 μm
    Optics Letters, 2009
    Co-Authors: Oliver D Mucke, S Alisauskas, A Pugžlys, Andrius Baltuska, D Sidorov, Peter Dombi, V Smilgevicius, J Pocius, Linas Giniūnas, R Danielius
    Abstract:

    Carrier-envelope phase-stable 4 μJ pulses at ~1.5 μm are obtained from a femtosecond Yb:KGW-MOPA-pumped two-stage optical parametric amplifier. This novel technology represents a highly attractive alternative to traditional Ti:sapphire front-ends for seeding multimillijoule-level optical parametric chirped-pulse amplifiers. For this task, we demonstrate stretching of the OPA output to ~40 ps and recompression to 33 fs pulse duration. As a stand-alone system, our tunable two-stage OPA might find numerous applications in Time-Resolved Spectroscopy and micromachining.

Takayoshi Kobayashi - One of the best experts on this subject based on the ideXlab platform.

  • use of ultrafast Time Resolved Spectroscopy to demonstrate the effect of annealing on the performance of p3ht pcbm solar cells
    ACS Applied Materials & Interfaces, 2015
    Co-Authors: Yuting Wang, Meihsin Chen, Chaoting Lin, Jianjhih Fang, Chejui Chang, Chihwei Luo, Atsushi Yabushita, Takayoshi Kobayashi
    Abstract:

    The organic solar cells of heterojunction system, ITO/PEDOT:PSS/P3HT:PCBM/Al, with a thermal annealing after deposition of Al exhibit better performance than those with an annealing process before deposition of Al. In this study, ultrafast Time-Resolved Spectroscopy is employed to reveal the underlying mechanism of annealing effects on the performance of P3HT:PCBM solar cell devices. The analyses of all decomposed relaxation processes show that the postannealed devices exhibit an increase in charge transfer, in the number of separated polarons and a reduction in the amount of recombination between excited carriers. Moreover, the longer lifeTime for the excited carriers in postannealed devices indicates it is more likely to be dissociated into photocarriers and result in a larger value for photocurrent, which demonstrates the physical mechanism for increased device performance.