Showing papers on "Excimer published in 1981"
TL;DR: In this paper, a new technique for the study of excited state spectra is introduced, which relies on the fully resonant coherent Stokes light generation which is shown to display peaks at excited state vibrational intervals even though there is initially no population in these levels.
75 citations
TL;DR: In this paper, the ratio of excimer to monomer fluorescence intensity was used as a probe of the conformational transitions in these molecules and four solvents were used in the studies.
Abstract: Because excimer formation occurs by the rotation of bonds to bring two adjacent chromophores into a coplanar arrangement, the ratio of excimer to monomer fluorescence intensity (I/sub E//I/sub M/) was used as a probe of the conformational transitions in these molecules. Four solvents were used in the studies.
45 citations
44 citations
TL;DR: Forster's kinetics were determined by the steady state and time-resolved fluorescence measurements as discussed by the authors, and the results suggest that intramolecular excimer formation is directly controlled by the rotational relaxation processes of the molecules from their neighboring conformations to the excimer conformation.
Abstract: Various dinaphthylalkanes in which two naphthyl groups are separated by three carbon atoms were prepared, and intramolecular excimer formation was investigated All rate constants in Forster’s kinetics were determined by the steady state and time-resolved fluorescence measurements A large difference in the association rate constant was observed with variation of molecular structure The results suggest that intramolecular excimer formation is directly controlled by the rotational relaxation processes of the molecules from their neighboring conformations to the excimer conformation A large formation rate (79×108 s−1 at 25 °C) was observed for meso-2,4-dinaphthylpentane, the rate for the racemo isomer being found to be one tenth of that for the meso isomer This indicates that the isotactic sequence in vinyl aromatic polymers plays an important role in the intramolecular excimer formation
36 citations
TL;DR: In this article, a 26 ps pulse of 347.2 nm light from a mode-locked ruby laser was used to photolyze benzene, bromobenzene, and toluene.
35 citations
30 citations
29 citations
27 citations
TL;DR: In this article, a study of monomer, dimer and excimer emission, absorption and excitation spectra shows that the excited dimer emission is transformed into excimer emissions at higher temperatures.
27 citations
TL;DR: The fluorescence from poly(N-vinylcarbazole) has been examined over the temperature range 200-295 K, using time-resolved and steady-state fluorescence spectroscopy.
Abstract: The fluorescence from a solution of poly(N-vinylcarbazole) has been examined over the temperature range 200–295 K, using time-resolved and steady-state fluorescence spectroscopy. At all temperatures the emission could be best described by a three-component fluorescence decay function, the derived lifetimes being assigned to three independent excimer groups. Some conclusions are drawn concerning the origins, interconversion between, and dissociation of, these species.
27 citations
TL;DR: In this paper, the time-of-flight spectra of photofragments produced by a one and two-photon dissociation of NOCl by 5 eV (248 nm) and 6.4 eV(193 nm) photons from an excimer laser have been measured.
TL;DR: In this paper, measurements of fluorescence spectra and fluorescence quantum yields associated with 1,3bis(9-anthryl)-1,1,3,3-tetra-methyldisiloxane and its photoisomer indicate that photochemistry occurs from an unsymmetrical excimer.
TL;DR: In this article, the authors investigated the process leading to the production and removal of the triatomic excimer Xe2Cl* subsequent to short duration electron beam excitation of Ar/Xe/CCl4 mixtures.
Abstract: Processes leading to the production and removal of the triatomic excimer Xe2Cl* subsequent to short duration electron beam excitation of Ar/Xe/CCl4 mixtures have been investigated. The radiative lifetime of Xe2Cl* has been measured to be 135 (+70−60) ns. Formation of the excimer has been shown to occur principally via a termolecular reaction involving XeCl*. Rate constants for the formation and collisional quenching of Xe2Cl* by CCl4, Xe, and Ar have been determined.
TL;DR: In this article, measurements of excimer:monomer fluorescence intensity ratios for two pyrene derivatives, 1,3-dipyrenylpropane and 1,10-dippyrenyldecane, in two different types of mixed solvent are reported.
TL;DR: In this paper, the authors used a series of extrapolation procedures to derive individual rate constants in the photophysical reaction scheme governing intramolecular excimer formation, in which the dependence upon local chromophore concentration within the polymer coil is removed.
TL;DR: In this paper, the authors show that 1,3-bis(4-methoxy-1-naphthyl)propane and 1, 3-bis (4-hydroxy-1 naphthsyl)-propane (BHNP) give fluorescence spectra showing the existence of two types of excimer: one with a peak at ≈ 410 nm (normal excimer) and the other at ∼ 370 nm (second excimer), the fluorescence from the second excimer increases with decreasing temperature of the solution, but disappears in the
TL;DR: In this article, the dynamics of excimer formation, excimer migration, and excimer dissociation in β-9,10-dichloroanthracene crystals were investigated by means of picosecond time-resolved fluorescence spectroscopy.
TL;DR: In this article, the photophysical properties of head-to-head polystyrene, block copolymers poly(butadiene- b -styrene) and polystyrenes of various sequence length of styrene chromophores were investigated.
TL;DR: Whereas both α- and β-cyclodextrin significantly inhibit intramolecular excimer formation of bis-(4-biphenylmethyl)ammonium chloride, γ-cyclodesxtrin enhances it considerably, indicating its ability to induce a conformational change in a molecule by forming an inclusion complex.
Abstract: Whereas both α-and β-cyclodextrin significantly inhibit intramolecular excimer formation of bis-(4-biphenylmethyl)ammonium chloride, γ-cyclodextrin enhances it considerably, indicating its ability to induce a conformational change in a molecule by forming an inclusion complex.
TL;DR: In this article, a radiative energy transfer is suggested from polystyrene to poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), which absorbs at 319 nm.
Abstract: By fluorescence spectroscopy it is possible to investigate some of the photophysical processes, particularly the energy transfer, that occur during the photo-oxidative degradation of polystyrene (PS), poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), and homogeneous blends of these. In connection with the irradiation, a part of the absorbed energy is transferred from excited phenyl groups in PS to PPO. The decrease in PS excimer fluorescence at 319 nm by admixture of PPO is greater than expected from the absorption of PPO at the excitation wavelength. A radiative energy transfer is suggested from PS to PPO which absorbs at 319 nm. Energy transfer also occurs to groups formed during photo-oxidation. The quenching of PS excimer fluorescence during the process has been studied for both the homopolymer and the blends, and in all cases the reactions occurring during photo-oxidation result in marked quenching at 319 nm.
TL;DR: In this article, it is proposed that excimer is formed by rotation of a pendant excited phenyl group with a face-to-face conformation with its nearest neighbour.
TL;DR: In this article, the fluorescence behavior of a series of acenaphthylene/methyl methacrylate copolymers covering a wide range of intramolecular chromophore compositions has been examined using pulsed laser excitation.
TL;DR: In this article, the photoluminescence characteristics of 2-vinylnaphthalene-styrene copolymers were studied under photostationary and transient conditions.
Abstract: The photoluminescence characteristics of 2-vinylnaphthalene–styrene copolymers were studied under photostationary and transient conditions. Kinetic analysis of the monomer and the excimer emission was carried out, where the migration rate of excitation energy kt and the excimer formation rate of an adjacent pair of naphthalene units on the copolymer chain k21 were treated. Observed decay curves and quantum yields were in agreement with those calculated by the kinetic equations, and the rate constants were obtained: kt=3×108 s−1, k21=2×108 s−1. The results indicate that the fast migration of excitation energy brings about the quenching of the excited monomer state, and causes the efficient intramolecular excimer formation.
TL;DR: In this paper, the B→X band of Xef at 352 nm has been pumped in a longitudinal low-pressure discharge, and low power, 20nsec laser pulses of high beam quality have been generated.
Abstract: Results of a new excitation technique for excimer lasers are reported. The B→X band of Xef at 352 nm has been pumped in a longitudinal low‐pressure discharge. Low‐power, 20‐nsec laser pulses of high beam quality have been generated.
TL;DR: The rate constants for bimolecular quenching of Ar (1s) resonance state and metastable atoms by N2, H2, and O2 have been measured by fast absoprtion spectrophotometry at argon pressures in the 102-103 Torr region at 298 K.
Abstract: Rate constants for bimolecular quenching of Ar (1s) resonance‐state and metastable atoms by N2, H2, and O2 have been measured by fast absoprtion spectrophotometry at argon pressures in the 102–103 Torr region at 298 K. ’’Three‐body’’ quenching attributed to collisional relaxation of vibrationally excited dissociative excimer molecules by molecular quenching agents has been observed to occur efficiently for all Ar (1s) atoms in the presence of H2 and O2, but only for the resonance‐state Ar (1s) species in the presence of N2. A discussion and analysis of the temporal behavior and the yield of Ar2 (3S+u) molecules in the context of the mechanism for Ar (1s) atom decay and excimer formation indicates that the predominant precursors of the first triplet argon excimer in Ar/N2 mixtures are probably Ar (3P2) atoms and Ar2 van der Waals molecules, the latter through the agency of N2 (C 3Ru) at higher N2 concentrations.
TL;DR: In this article, the possibility of realizing an optically pumped alkali noble gas excimer laser is discussed, and experimental details for NaI-Xe and CsI-xe systems excited by 193 nm ArF or 249 nm KrF laser radiation are given.
Abstract: Alkali noble gas excimer molecules are produced by photodissociation of alkali halogen vapor in a high-pressure noble gas atmosphere. Experimental details for NaI-Xe and CsI-Xe systems excited by 193 nm ArF or 249 nm KrF laser radiation are given, and the possibility of realizing an optically pumped alkali noble gas excimer laser is discussed.
TL;DR: In this paper, the authors show that α,α-dinaphthylalkanes from triplet excimers can be formed instantaneously with excitation by a nanosecond laser pulse (≈ 17 ns pulse width).
TL;DR: In this article, a model was proposed to account for changes in the intensity of excimer to monomer fluorescence emission with varying molecular weight and copolymer composition, and satisfactorily accounts for the excimer;'monomer;'fluorescence ratio without involving the concept of energy migration.