Topic
Excimer
About: Excimer is a research topic. Over the lifetime, 3725 publications have been published within this topic receiving 75104 citations.
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TL;DR: In this paper, photo-induced electron transfer (PET) was investigated by monitoring the quenching of monomer and excimer pyrene fluorescence in mixed LB films containing different concentrations of C 60.
28 citations
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TL;DR: Parker and Hatchard as discussed by the authors showed that delayed fluorescence exhibited by dissolved aromatic hydrocarbons A originates in the interaction of two triplet states, and that at low light intensities the overall process 1, followed by 2, is controlled by the first-order process 3 which is almost entirely responsible for triplet state decay under these conditions.
Abstract: Parker and Hatchard1 have convincingly demonstrated that delayed fluorescence exhibited by dissolved aromatic hydrocarbons A originates in the interaction of two triplet states, and that at low light intensities the overall process 1, followed by 2, is controlled by the first-order process 3 which is almost entirely responsible for triplet state decay under these conditions. To account for the presence of the dimer band in the delayed fluorescence spectrum of pyrene2, these authors3 suggest that process 1 involves Colpa's doubly-excited state 1A2 ** and the excimer 1A2* as intermediates, that is: where the energy-dependent process 1c competes with excimer fluorescence, process (4). This mechanism accounts for the observation3 that the ratio of intensities ID/IM of dimer to monomer bands in the delayed spectrum approaches a limiting non-zero value at zero concentration of A at room temperature; moreover, it requires a negative temperature coefficient of ID/IM which is indeed observed above 0° C as shown in Fig. 1.
28 citations
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TL;DR: Experiments utilizing gas chromatography have indicated that the vapour-phase photoproducts liberated during excimer laser tissue ablation are indistinguishable from those observed following continuous wave laser irradiation or flame torching of cardiovascular tissue.
Abstract: Previous investigations have demonstrated in vitro that the excimer laser may be used to accomplish cardiovascular tissue ablation without causing thermal injury to boundary sites. Initial investigations suggested that results achieved with the excimer laser were related to photochemical breaking of molecular bonds, rather than thermal degradation. More recent investigations, however, have suggested that the mechanism of excimer tissue ablation may not be unique. Results indistiguishable from those accomplished with the excimer laser have been reproduced using both visible and infrared wavelengths. Experiments utilizing gas chromatography have indicated that the vapour-phase photoproducts liberated during excimer laser tissue ablation are indistinguishable from those observed following continuous wave laser irradiation or flame torching of cardiovascular tissue. While photoemission spectroscopic analysis has identified free radicals released in gas phase during excimer laser ablation, electron paramagnetic resonance spectroscopy has similarly identified free radicals released in solution during continuous wave laser ablation; while these two techniques may detect different types of radicals with different kinetic behaviour, these results indicate, that the finding of free radical photoproducts per se during laser ablation does not necessarily exclude a non-thermal mechanism. Finally, plasma-mediated photodisruption represents a third alternative to explain pulsed laser ablation; experiments are required, however, to define whether plasma generated during pulsed laser irradiation is central to the ablation process, or represents an epiphenomenon.
28 citations
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TL;DR: The structural changes in the collagen fibrils of the corneal stroma, especially the increase in interfibrillar distances and the disordered arrangement, were associated with cornean haze after excimer laser keratectomy.
Abstract: Purpose: To investigate the structural changes in corneal stromal collagen fibrils after excimer laser keratectomy in relation to the degree of corneal haze. Setting: University of Tokyo Hospital, Tokyo, Japan. Methods: Corneal haze was quantitatively measured by analyzing the light scattering in Scheimpflug images of the corneas of white rabbits after excimer laser keratectomy. Collagen fibril structure was examined using scanning electron microscopy after chemical digestion with sodium hydroxide solution; the same specimens were examined by transmission electron microcopy after re-embedding. Results: Corneal haze reached a peak 4 weeks after excimer laser keratectomy and then gradually decreased, The collagen fibrils of the normal cornea were regularly arranged parallel to the surface of the cornea, with small interfibrillar distances. After excimer laser keratectomy, the arrangement was highly disordered, with increased interfibrillar distances. These structural changes were most prominent 4 weeks after excimer laser keratectomy. Conclusion: The structural changes in the collagen fibrils of the corneal stroma, especially the increase in interfibrillar distances and the disordered arrangement, were associated with corneal haze after excimer laser keratectomy.
28 citations
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TL;DR: In this paper, the authors measured the fluorescence behavior of poly(ethylene terephthalate) (PET) films prepared by using a spin-casting method and found that the wavelength of the peak was dependent on the casting temperature, T cast.
28 citations