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Vibrational Dephasing along the Reaction Coordinate of an Electron Transfer Reaction
No full textThe role of molecular vibration in photoinduced electron transfer (ET) reactions has been extensively debated in recent years. In this study, we investigated vibrational wavepacket dynamics in a model ET system consisting of an organic dye molecule as an electron acceptor dissolved in various electron donating solvents. By using broad band pump-probe (BBPP) spectroscopy with visible laser pulses of sub-10 fs duration, coherent vibrational wavepackets of naphthacene dye with frequencies spanning 170-1600 cm^-1were observed in the time domain. The coherence properties of 11 vibrational modes were analyzed by an inverse Fourier filtering procedure, and we discovered that the dephasing times of some vibrational coherences are reduced with increasing ET rates. Density functional theory calculations indicated that the corresponding vibrational modes have a large Huang-Rhys factor between the reactant and the product states, supporting the hypothesis that the loss of phase coherence along certain vibrational modes elucidates that those vibrations are coupled to the reaction coordinate of an ET reaction
Solvent-dependent photo-induced dynamics in a non-rigidly linked zinc phthalocyanine-perylenediimide dyad probed using ultrafast spectroscopy
Get PDFIn this work, we characterize the energy and electron transfer kinetics of a zinc phthalocyanine-perylenediimide dyad (ZnPc-PDI) in various solvents using steady-state and tunable narrowband pump-probe spectroscopy. We fit the ultrafast data with global analysis techniques and find that upon excitation of the PDI moiety (pump pulse at 540 nm), the excitation energy transfer (EET) rate to the ZnPc moiety displays a solvent sensitivity that we attribute to changes in the relative equilibrium moiety orientation. We rationalize these observations by considering the nature of the non-rigid bridge used to link the two moieties as well as the degenerate nature of the Q band transitions in the ZnPc species. By tuning the pulse into resonance with the ZnPc Q band (685 nm) we can directly photo-induce an electron transfer (ET) process back to the PDI moiety. Employing the same global analysis, we find that the dynamics of the ultrafast electron transfer are completely kinetically controlled according to the Bixon-Jortner model of barrierless solvent-controlled curve crossing, while the recombination to reform the ground state is well-described using the static energetic picture according to Marcus theory
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
New directions in the ultrafast spectroscopy of organic chromophores
No full textThe photophysics of organic chromophores is a gargantuan field of study, with various subfields encompassing various spectroscopic techniques, different chromophore types and multichromophoric systems, and materials with practical implications. In even these broad subthemes, ultrafast spectroscopy has played a central role in understanding their photoinduced dynamics, either to build upon our fundamental knowledge of chemical dynamics or to characterize and design more efficient optoelectronic devices. One simple question to ask is: what’s next for ultrafast spectroscopy? This Thesis begins exploring the emerging uses of ultrafast spectroscopy in the context of developing technologies and new experimental techniques. A historical context to ultrafast spectroscopy, focusing on the evolution of the systems studied over various time-periods and motivating the next generation of spectroscopic targets, is presented in Chapter 1. In Chapter 2, sufficient background and theoretical details towards understanding the basics of the photophysics covered in this Thesis is provided. Chapters 3 and 4 reflect early PhD studies on the photophysical dynamics of model chromophore systems, with the latter being of added interest to not only the organic photovoltaics community as well as to the recent development in organic nanoparticles for phototheranostics. Chapter 5 explores novel high magnetic field effects on diamagnetic organic chromophores in an organic nanoparticle, a study with numerous firsts for organic magnetoscience and boasting experiments with femtosecond time resolution at magnetic fields as high as 25 T. Chapter 6 concludes the thesis with a deep-dive into the photophysics of newly discovered photoenzymes, a study which elucidates the role of the active site environment on the photophysical properties of redox active flavoproteins
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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