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Optical limiting of transition metal-phthalocyanine complexes: A photochromic effect involving the excited state of the conjugated molecule
No full text10.1080/15421400590947423Molecular Crystals and Liquid Crystals431259/[559]-274/[574]MCLC
Physical properties of phthalocyanine based materials
No full textCHAPTER ORGANIZATION
1,2-Definitions of physical properties of Pcs
3- Structural features
a) Molecular geometries
b) Spatial arrangements of molecules
4-Electronic structure of Pcs
a) Electrons in p-type orbitals of gaseous species
b) Electrons in low lying energy states of gaseous species
c) Electronic structure in solid Pcs
5-Optical absorption of Pcs
6-Electrical conduction in Pcs
7-Photoconduction in Pcs
8-Nonlinear optical (NLO) properties
a) Introduction
b) Optical limiting (OL)
c) Pcs for OL
d) NLO of crystal
Indium phthalocyanines with different axial ligands: A study of the influence of the structure on the photophysics and optical limiting properties.
No full textThe photophysical properties of four axially substituted indium phthalocyanines, namely, 2,(3)-tetra-tertbutyl-
phthalocyaninato indium chloride (1), 2,(3)-tetra-[(3,5-di-tert-butyl)-phenyloxy]-phthalocyaninato indium
bromide (2), 2,(3)-tetra-[(3,5-di-tert-butyl)-phenyloxy]-phthalocyaninato indium iodide (3), and 2,3-octa-[(2-
hexyl)-ethyloxy]-phthalocyaninato indium trifluoroacetate (4), have been investigated, and their optical limiting
properties with nanosecond light pulses were evaluated. All complexes behave as reverse saturable absorbers
in the range of 400-625 nm due to a triplet-triplet excited-state transition. Excited-state absorption cross
sections and triplet state lifetimes are not significantly affected by the nature of the axial ligand. On the other
hand, remarkable differences in the variation of nonlinear transmittance are observed for 1-4 due to significantly
different intersystem crossing rates. Heavier axial ligands in phthalocyanines 2 and 3 produce the largest
variations of nonlinear transmission (heavy-atom effect). Complex 1 in polystyrene matrix shows reversible
nonlinear absorption when incident fluence does not exceed 0.025 J cm-2
Demonstration of the optical limiting effect for an hemiporphyrazine
No full textThe hemiporphyrazine complex 9,22-bis(dibutoxy)hemiporphyrazinato
chloroindium(III) (1) is one of the few examples
for this class of compounds, which displays the nonlinear
optical effect of reverse saturable absorption for nanosecond
laser pulses in the visible spectrum. The high linear transmission
combined with the fast switching into a strongly absorbing
excited state in the same spectral range (400–650 nm), renders
the studied hemiporphyrazine an ideal material for the passive
shuttering of pulsed radiations
Large two-photon absorption cross sections of hemiporphyrazines in the excited state: The multiphoton absorption process of hemiporphyrazines with different central metals
No full textA series of five hemiporphyrazines (Hps) with different coordinating central atoms (H2, GeCl2, InCl, Pt, Pb), and the acyclic derivative 1,3-bis-(6′-amino-4′-butoxy-2′-pyridylimino)-1,3-dihydroisoindoline have been synthesized and their multiphoton absorption properties examined at the second harmonic frequency of the Nd:YAG laser in the nanosecond time regime. Metal-free and platinum Hps display saturation of optical transmittance within incident fluence values of 6 J cm−2. Comparison with other similar molecular structures like phthalocyanines and related molecules shows that Hps are strong nonlinear absorbers. The experimental curves of nonlinear transmission at 532 nm have been fitted by means of a three-level model with the occurrence of simultaneous two-photon absorption from an excited state. In the sole case of the InCl complex we found that a five-level model is needed because of the participation of triplet states. Contrary to phthalocyanines, naphthalocyanines, and porphyrins, a heavy central atom does not improve the nonlinear absorption properties since a different excited states dynamic is involved. The large nonlinear absorption of Hps combined with the very small absorption in the visible spectral range makes these molecules a very interesting class of molecules for nonlinear optical applications
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Variations on the Author
Full text link“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
Full text linkWe 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
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