Showing papers on "Excimer published in 1985"
TL;DR: Preliminary experiments indicate that the excimer laser vaporizes tissue in a manner different from that of the continuous wave Nd:YAG or argon ion laser.
333 citations
TL;DR: The pulsed ultraviolet excimer laser has been used to produce tissue ablation with a high degree of precision and with minimal thermal damage to adjacent structures, and threshold fluence for corneal and lens ablation was higher at 248 nm than at 193 nm.
306 citations
TL;DR: The paucity of pathologic alterations observed after excimer irradiation of cardiovascular tissue may prove beneficial in precisely controlling laser ablation of pathological tissue without injury to the surrounding normal tissue.
190 citations
TL;DR: In this article, the time dependence, rise and decay of α-perylene following ps-pulse excitation was investigated as a function of temperature (4.2-300 K).
109 citations
98 citations
TL;DR: In this paper, the fluorescence decays of 1,3-di(1-pyrenyl)propane undergoing intramolecular excimer formation can be fitted to a sum of three exponentials.
75 citations
TL;DR: It is shown that the presence of appreciable excimer fluorescence at temperatures below the N----X pretransition (initial excimer) is due to perturbation of the TM chain-chain interaction by the pyrenes at Cys-190, and that F-actin stabilizes tropomyosin by inhibiting the N ----X transition.
Abstract: The fluorescence of pyrene-TM [rabbit skeletal tropomyosin (TM) labeled at Cys with N-(1-pyrenyl)maleimide] consists of monomer and excimer bands [Betcher-Lange, S., & Lehrer, S.S. (1978) J. Biol. Chem. 253, 3757-3760]; an increase in excimer fluorescence with temperature is due to a shift in equilibrium from a chain-closed state (N) to a chain-open state (X) associated with a helix pretransition [Graceffa, P., & Lehrer, S.S. (1980) J. Biol. Chem. 255, 11296-11300]. In this study, we show that the presence of appreciable excimer fluorescence at temperatures below the N----X pretransition (initial excimer) is due to perturbation of the TM chain-chain interaction by the pyrenes at Cys-190. Fluorescence and ATPase titrations indicated that the label caused a decrease in TM binding to F-actin primarily due to reduced end to end TM interactions on the actin filament. Under conditions where pyrene-TM was bound to F-actin, however, the excimer fluorescence did not increase with temperature, indicating that F-actin stabilizes tropomyosin by inhibiting the N----X transition. The binding of myosin subfragment 1 (S1) to pyrene-TM-F-actin at low ratios to actin caused time-dependent changes in fluorescence. After equilibrium was reached, the initial excimer fluorescence was markedly reduced and remained constant over the pretransition temperature range. Further stabilization of tropomyosin conformation on F-actin is therefore associated with S1 binding. Effects of the binding of S1 to the F-actin-tropomyosin thin filament on the state of tropomyosin were studied by monitoring the monomer fluorescence of pyrene-TM.(ABSTRACT TRUNCATED AT 250 WORDS)
46 citations
TL;DR: In this article, potential curves, transition wavelengths, radiative lifetimes, and cross sections for stimulated emission for several alkali halide ions are calculated for both VUV and XUV regions.
Abstract: Optical transitions in ionic excimer molecules seem to be suitable candidates for lasers in the VUV and XUV region. Potential curves, transition wavelengths, radiative lifetimes, and cross sections for stimulated emission are calculated for several alkali halide ions. In addition, possible laser transitions in rare gas halide ions are briefly discussed.
43 citations
TL;DR: In this paper, it was shown that 1,3-di(2-pyrenyl)propane in methylcyclohexane can be fitted with two exponentials having the same decay parameters for the excimer and the monomer.
42 citations
TL;DR: In this paper, a picosecond laser pulse at the wavelength of no appreciable ground-state absorption has been used to excite benzene and alkylbenzenes homogeneously in the neat liquid state and investigate their photophysical and photochemical primary processes by spectral measurements.
Abstract: Ultraviolet multiphoton excitation with a picosecond laser pulse at the wavelength of no appreciable ground-state absorption has been used to excite benzene and alkylbenzenes homogeneously in the neat liquid state and to investigate their photophysical and photochemical primary processes by picosecond time-resolved transient absorption spectral measurements. The excimer formation processes in neat liquid benzenes excited by two-photon absorption of the 355-nm picosecond pulse from a Nd/sup 3 -/:YAG laser have been confirmed to proceed via ionization and recombination processes, and the lifetime of the ionized (ion pair) state has been determined to be 10-20 ps in neat benzene. 26 references, 4 figures, 4 tables.
38 citations
TL;DR: The fluorescence decays of pyrene in small and large unilamellar L,α-dipalmitoylphosphatidylcholine vesicles have been investigated as a function of probe concentration and temperature and the fluorescence decay kinetics are compatible with the excimer formation scheme which is valid in an isotropic medium.
Abstract: The fluorescence decays of pyrene in small and large unilamellar L, alpha-dipalmitoylphosphatidylcholine vesicles have been investigated as a function of probe concentration and temperature. When the molar ratio of pyrene to phospholipid equals 1:3000, no excimer emission is observed and the fluorescence decays are mono-exponential. When this ratio is equal to or higher than 1:120, excimer formation is observed. Above the phase transition temperature the observed fluorescence decays of monomer and excimer can be adequately described by a bi-exponential function. The monomer decays can be equally well fitted to a decay law which takes into account a time-dependence in the probe diffusion rate constant. The fluorescence decay kinetics are compatible with the excimer formation scheme which is valid in an isotropic medium. The excimer lifetime and the (apparent) rate constant of excimer formation have been determined as a function of probe concentration at different temperatures above the phase transition temperature. The activation energy of excimer formation is found to be 29.4 +/- 1.3 kJ/mol. In small unilamellar vesicles the diffusion constant associated with the pyrene excimer formation process varies from 8.0 X 10(-7) cm2/s at 40 degrees C to 2.2 X 10(-6) cm2/s at 70 degrees C. Below the phase transition temperature the monomer decays can be described by a decay law which takes into account a time dependence of the rate constant of excimer formation. The lateral diffusion coefficient of pyrene calculated from the decay fitting parameters of the monomer region varies from 4.0 X 10(-9) cm2/s at 20 degrees C to 7.9 X 10(-8) cm2/s at 35 degrees C. No significant difference could be observed between the pyrene fluorescence decay kinetics in small and large unilamellar vesicles.
TL;DR: In this paper, pyrene-containing phospholipid analogues have been studied for their absorption in the range of 300-650 nm, which indicates the very close proximity of the pyrene moieties, yet without significant ground state interaction, as suggested by the similarity to the absorption spectra of pyrene in organic solvents.
Patent•
06 Dec 1985
TL;DR: In this article, a fluorescent lamp is described in which spontaneous excimer UV emission in an inner tube results from reacting an inert gas molecule with a halide molecule in the excited state.
Abstract: A fluorescent lamp is described in which spontaneous excimer UV emission in an inner tube results from reacting an inert gas molecule with a halide molecule in the excited state. The UV emission travels through the inner tube envelope to an outer tube and is absorbed by a fluorescent material, i.e., phosphor, to produce visible light which passes through the outer tube envelope. The halide may be supplied by metal halide pellets or liquid droplets, which when heated by an initial discharge through an inert gas, produces metal halide vapors which dissociate and combine with the inert gas (Xe, Ar, Ne, Kr) in the excited state and result in UV excimer emission.
TL;DR: In this paper, the mechanism for production of electronically excited photofragments from the title molecules was investigated using two excimer lasers in a pump-probe experiment, and it was shown that secondary excitation of primary photofrigments is involved.
TL;DR: In this article, the radiative decay of the excimer state CsF + isoelectronic to XeF was observed and the failure to detect the corresponding transitions in CsCl + is discussed.
TL;DR: In this article, temperature dependent build-up of the excimer fluorescence in pyrene occurring at the picosecond time scale is reported, where the observed rise time is constant below the crystal phase transition temperature Tp' abruptly increases at T=Tp and monotonically decreases towards room temperature.
TL;DR: In this article, the photophysical properties of poly[2-(9-carbazolyl)ethyl methacrylate] film have been studied and shown to have a clear monomer fluorescence spectrum from carbazole chromophores.
TL;DR: Successful oscillation of a tunable, high-power argon excimer laser is reported and the possibility of frequency conversion of the argonexcimer laser radiation to other wavelengths by a stimulated Raman scattering process is discussed.
Abstract: Successful oscillation of a tunable, high-power argon excimer laser is reported. The wavelength was tuned from 124.5 to 127.5 nm with a spectral width of 0.3 nm. The output power of 2.2 MW, obtained at the line center, is 3 orders of magnitude larger than the value reported previously by Wrobel et al. [Appl. Phys. Lett. 36, 113 (1980)]. The possibility of frequency conversion of the argon excimer laser radiation to other wavelengths by a stimulated Raman scattering process is discussed.
TL;DR: The role of pressure applied to dimerization reactions appears to follow the same topochemical principles applied to chemical reactivity in the solid state as discussed by the authors, where the trans (head-to-tail) excimer is active and is the intermediate of the dimer produced by irradiation.
TL;DR: The results suggest that a Ca2+-induced structural change in the TnI-binding region of TnC could be transmitted to TnT by affecting theTnT-binding area of TNI as part of the chain of events in the regulation of muscle contraction.
TL;DR: In this paper, the cycloaddition intramoleculaire de l'hexadiene-1,5 and de heptadiene -1,6 conduisant respectivement au bicyclo [2.1] hexane and au bicycleo [3.2] heptane.
Abstract: Etude relative a la cycloaddition intramoleculaire de l'hexadiene-1,5 et de heptadiene-1,6 conduisant respectivement au bicyclo [2.1.1] hexane et au bicyclo [3.2.0] heptane. Mecanisme etabli par l'etude de diagrammes de correlation d'etats et d'orbitales
TL;DR: In this paper, the absorption cross section for the lowest-lying, bound excited state (4 2Γ) of Xe2Cl has been measured at several wavelengths in the ultraviolet (UV).
Abstract: The absorption cross section for the lowest‐lying, bound excited state (4 2Γ) of Xe2Cl has been measured at several wavelengths in the ultraviolet (UV). Temporally isolating the excited Xe2Cl species in Xe/Cl2 gas mixtures has been accomplished by producing XeCl molecules in the B state by photoassociation [Xe+Cl+ℏω → XeCl(B)] at λ=308 nm. Collisional mixing of the lowest lying ion pair states of the excimer subsequently forms the XeCl species in its C state. Following the formation of Xe2Cl* from XeCl(B,C) by a three‐body collision, the long radiative lifetime of the trimer (>200 ns) relative to those for the XeCl B and C levels is exploited to ensure that the triatomic molecule is the predominant species when the experiments are performed. A second UV laser pulse depletes the Xe2Cl(4 2Γ) population by photoexcitation [as evidenced by the sudden suppression of the 4 2Γ → 1 2Γ blue‐green (λ∼485 nm) fluorescence] and the absorption cross section is determined from the dependence of the degree of fluorescen...
Patent•
22 Aug 1985
TL;DR: In this paper, a fluorescent monomer and a quencher are added to a fluid, and the monomer is excited by directing an energy source of a proper wavelength at the fluid.
Abstract: A method for determining the temperature of a fluid particularly adapted to the determination of droplet temperatures. A fluorescent monomer and a quencher are added to a fluid and the monomer is excited by directing an energy source of a proper wavelength at the fluid. The excited monomer then combines with the quencher to produce a fluorescent exciplex in the fluid. The temperature of the fluid is determined by detecting the fluorescence from the excited monomer and exciplex in the fluid. The ratio of fluorescence of these species provides data from which the temperature can be determined.
TL;DR: In this paper, a tunable dye laser pulse was used to determine the time dependence of the absolute concentration of XeCl* excimer molecules in the plasma of an electric-discharge xeCl laser.
Abstract: The plasma of an electric-discharge XeCl laser was investigated by the method of absorption probing with tunable dye laser pulses. The duration of a probe pulse was 7 nsec and the half-width of the laser line was 15 pm. A synchronization system made it possible to shift the probe pulse on the time scale relative to the discharge and this could be done with an accuracy of 3 nsec. The absorption spectra were determined in the range 335–610 nm for a mixture of the composition He:Xe:HCl = 550:8:1 at a pressure of p = 2.2 atm. The time dependences of the absolute concentrations of Xe*, He*, Xe+*, and Cl− were obtained. The dynamics of population of excited atoms and ions was analyzed. Amplification of a small signal was used to determine the time dependence of the absolute concentration of XeCl* excimer molecules. It was found that during the initial stage of the discharge the dominant XeCl* formation channel was a harpoon reaction, whereas during later stages the ion–ion recombination process predominated.
Patent•
10 Oct 1985
TL;DR: An excimer optical display as discussed by the authors is a plasma panel device having therein a mixture of gas comprising xenon and molecular fluorine and a selected amount of other gases forming XeF excimer molecules such that the color of fluorescence is adjustable over a broad spectrum by selection of the gas mixture constituents.
Abstract: An excimer optical display includes a plasma panel device having therein a mixture of gas comprising xenon and molecular fluorine and a selected amount of other gases forming XeF excimer molecules such that the color of fluorescence is adjustable over a broad spectrum by selection of the gas mixture constituents.
TL;DR: In this article, the fluorescence properties of α,ω-dimorpholinoalkanes have been studied in which the amino groups include diethylamino, pyrrolidin, piperidino, and morpholino residues.
Abstract: The fluorescence properties of a number of α,ω-diaminoalkanes have been studied in which the amino groups include diethylamino, pyrrolidino, piperidino, and morpholino residues. Intramolecular excimer formation was usually observed when di- and tri-methylene chains separated the amino groups. α,ω-Dimorpholinoalkanes having chain lengths of varying size between the morpholino groups, exhibited fluorescent excimer formation. Owing to the high concentrations employed it could not be ascertained whether the emission was the result of inter- or intra-molecular complex formation. In all cases the excimer fluorescence was considerably red shifted by a change of solvent from cyclohexane to tetrahydrofuran. This solvent dependency leads to the conclusion that amine excimers have some charge-transfer character.
TL;DR: In this paper, an excimer fluorescence technique for the study of polymer segment mobility has been developed and applied to pyrene-labeled poly(methyl methacrylate) and poly-methyl acrylate polymers in solution and the results of the study have been interpreted in terms of Kramers' theory for the crossing of a potential barrier by a particle embedded in a viscous medium.
TL;DR: In this article, a simple experimental technique based on relative measurements of the axial and sidelight fluorescence signals is reported for gain measurement in discharge excimer lasers, which shows a gain of 15% cm-1, considerably higher than previously reported.
01 Jul 1985
TL;DR: In this article, the authors investigated pulsed excimer and CO2 laser annealing phenomena as a function of laser parameters in boron-implanted silicon, using cross-section transmission electron microscopy.
Abstract: We have investigated pulsed excimer and CO2 laser annealing phenomena as a function of laser parameters in boron‐implanted silicon, using cross‐section transmission electron microscopy. The depth of annealed regions or melting was found to increase linearly with the pulse energy density and inversely with the pulse duration. The threshold for melting and depth of the melted regions as a function of pulse energy density and duration were found to be in good agreement with heat‐flow calculations. Pulsed CO2 laser annealing required either high doping or substrate heating to increase free‐carrier absorption. The annealing results in both cases were consistent with a first‐order phase transformation involving melting.
TL;DR: In this paper, the radial distribution profiles of ground state atoms and/or ions for calcium, manganese and copper in an inductively coupled plasma have been measured using an excimer (XeCI) pumped dye laser as an excitation source of fluorescence.