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Showing papers on "Excimer published in 1971"


Journal ArticleDOI
TL;DR: Fluorescence spectra and lifetimes of carbazole, 1,3-bis(N carbazolyl)propane and poly(Nvinyl‐carbazole) have been studied as a function of pressure to 30 kbar at room temperature and 77°K polymer films show exclusively excimer fluorescence (τ=43 nsec) as mentioned in this paper.
Abstract: Fluorescence spectra and lifetimes of carbazole, 1,3‐bis(N‐carbazolyl)propane and poly(N‐vinyl‐carbazole) have been studied as a function of pressure to 30 kbar at room temperature and 77°K Polymer films show exclusively excimer fluorescence (τ=43 nsec) at room temperature This is not quenched at 77°K but appears together with a new emission (τ=12 nsec) attributed to traps arising from exciton coupling between adjacent carbazole chromophores The comparative P, T response of the three compounds suggests that excimers do not form between adjacent chromophores in the amorphous polymer

67 citations


Journal ArticleDOI
TL;DR: In this paper, it was shown that the 265 nm pulsed laser photolysis and pulse radiolysis of dilute solutions of benzene give rise to two transitory absorption spectra with maxima at 490 nm and 320 nm.

52 citations


Journal ArticleDOI
TL;DR: In this article, time-resolved fluorescence spectra were measured for pyrene and for the pyrene-N,N-dimethylaniline system in the range from 3 nsec to 150 nsec after the excitation by a nitrogen gas laser.

48 citations


Journal ArticleDOI
TL;DR: In this paper, the absorption and polarization spectra from the first excited singlet state of pyrene and the absorption spectrum of the pyrene excimer were obtained by laser flash spectroscopy using a frequency doubled ruby laser pulse of 6 nanoseconds halfwidth.

47 citations


Journal ArticleDOI
TL;DR: In this paper, the exciplex absorption spectra of pyrene, anthracene, biphenyl, and naphthalene with diethylaniline (DEA) as a common electron donor are recorded by applying pulse laser photolysis.
Abstract: Absorption spectra of the exciplexes of pyrene, anthracene, biphenyl, and naphthalene with diethylaniline (DEA) as a common electron donor are recorded by applying pulse laser photolysis. The numerous bands appearing in the spectra are analyzed and attributed to transitions from the emitting charge‐transfer state, (A−D+), to higher excited charge‐transfer states [(A−*D+) and (A−D+*)], as well as to locally excited states [(A*D) and (AD*)]. The results indicate that exciplex absorption spectroscopy may provide a new route to the experimental observation of excited molecular states (of D or A), which are not detectable in the ground state spectra of the corresponding molecules.

44 citations


Journal ArticleDOI
TL;DR: In this paper, the mixed delayed fluorescence due to the processes, (Remark: Graphics omitted.) in the following systems in ethanol solutions have been quantitatively investigated, a) 1) 9methylanthracene-anthracene, 2) 9-phenylthracen-anthricene, 3), 9-methylthricene-9-phenylanthricen, 4) anthracene -acridine, 5) 9 -methyi-thracenes-acridines, 6) eosin-anth
Abstract: The mixed delayed fluorescence due to the processes, (Remark: Graphics omitted.) in the following systems in ethanol solutions have been quantitatively investigated, a) 1) 9-methylanthracene-anthracene, 2) 9-phenylanthracene-anthracene, 3) 9-methylanthracene-9-phenylanthracene, 4) anthracene-acridine, 5) 9-methylanthracene-acridine, 6) 9-phenylanthracene-acridine. b) 7) eosin-anthracene, 8) proflavine-anthracene, 9) eosin-acridine. It has been found that for class a) in which the separations of singlet excited levels of A and B are less than a few times of kT, the delayed fluorescence of both components occur and the value of (pMA+pMB is close to that of the efficiency of a simple p-type delayed fluorescence, pA or pB. The delayed mixed excimer fluorescence also occurs in most cases. For class b) in which the level differences largely exceed kT, only the delayed fluorescence of the lower level component occurs. It has also been established that the delayed excimer fluorescence in a single component system...

33 citations



Journal ArticleDOI
TL;DR: In this paper, the characteristics of the electrogenerated chemiluminescence in dimethylformamide of pyrene, 1,2-benzpyrene, 3,4-benzinpyrene and dibenzo[a,lpyrene] generated with optimum conditions of applied potential are described.

20 citations


Journal ArticleDOI
TL;DR: In this paper, the decay times of excimer emission of pure and perylene doped pyrene crystals were measured by a pulse method and, thereby, the probability of energy transfer from the excimer to doped perylene molecules was obtained.
Abstract: The decay times of excimer emission of pure and perylene doped pyrene crystals were measured by a pulse method and, thereby, the probability of energy transfer from the excimer to doped perylene molecules was obtained. Furthermore, its temperature dependence was obtained. By the analysis of these results the diffusion coefficient D of the excimer migration in the pyrene crystal was obtained as D = D 0 exp (- E / k T ) ( D 0 =1.0×10 -2 cm 2 sec -1 and E =0.071 eV). It was confirmed that the excimer could migrate like an exciton in the pyrene crystal.

18 citations


Journal ArticleDOI
TL;DR: In this article, the authors examined previous results and theories concerning the emission of light from frozen solutions of pyrene in hydrocarbon solvents, and suggested that the results are due to the formation of Pyrene crystals, which exhibit?excimer? fluorescence.
Abstract: Previous results and theories concerning the emission of light from frozen solutions of pyrene in hydrocarbon solvents are examined in the context of the present experiments. It is suggested that the results are due to the formation of pyrene crystals, which exhibit ?excimer? fluorescence.

18 citations


Journal ArticleDOI
TL;DR: In this paper, the first excited state of a molecule containing n electrons should belong to the same point group as the ground state of another similar molecule with n + 1 or n + 2 electrons.

Journal ArticleDOI
TL;DR: In this article, a wide distribution of singlet and triplet trap depths and excimer conformations is indicated by the pressure modifications of the excimer fluorescence band, leading exclusively to excimer and delayer fluorescence.
Abstract: The compression of naphthalene crystals (to 30 kbar) at 77°K irreversibly, defects in the lattice. These defects capture singlet and triplet excitons, leading exclusively to excimer and delayer excimer fluorescence. Triplet trap depths of ∼600 cm−1 at 1 atm and ∼700 cm−1 at 30 kbar are estimated from the temperature dependence of the delayed excimer fluorescence. A wide distribution of singlet trap depths and excimer conformations is indicated by the pressure modifications of the excimer fluorescence band.

Journal ArticleDOI
TL;DR: In this article, the authors show that tetraphenyl compounds with Group IV and Group V atoms in solution show fluorescence and phosphorescence resembling benzene but in solids show a red shifted fluorescence.

Journal ArticleDOI
TL;DR: In this paper, the application of pressure to powdered pyrene was found to induce broad triplet excimer emission originating from lattice defects, and another type of defect was also created, giving rise to structured monomer emission.

Journal ArticleDOI
TL;DR: In this paper, the vapour phase u.v. absorption spectrum of 1,2,5thiadiazole near 2600 A has been shown to be π→π* in nature and to involve a planar ground state and a non-planar excited state having a barrier to in version of ca. 461 cm-1.
Abstract: The vapour-phase u.v. absorption spectrum of 1,2,5-thiadiazole near 2600 A has been shown to be π→π* in nature and to involve a planar ground state and a non-planar excited state having a barrier to in version of ca. 461 cm–1.

Journal ArticleDOI
TL;DR: In this article, triple energy transfer to a guest in a pyrene host matrix is used to locate the triplet excimer level in solid pyrene and the location is found to be between 15 800 cm −1 and 16 500 cm − 1.

Journal ArticleDOI
TL;DR: In this paper, the stabilisation enthalpies of two different kinds of triplet excimers of pyrene were calculated from the temperature dependence of the triplet lifetime.

Journal ArticleDOI
TL;DR: In this paper, the authors show that the ratio V of delayed monomer and excimer fluorescence intensities, on softening of a glassy solution with increasing temperature, first decreases and then increases at higher temperatures, after having passed through a minimum.

Journal ArticleDOI
TL;DR: In this paper, it is shown that the excimer phosphorescence maxima shifts substantially to lower energy from crystal to solid solution, probably due to a reduction in the repulsive potential in the dimer ground state from solution to crystal.
Abstract: Evidence is presented to confirm triplet excimer emission from halogenated benzene crystals. The emission is not due to photochemical imurities or other effects provided the samples are in vacuum. It is shown that the excimer phosphorescence maxima shifts substantially to lower energy from crystal to solid solution, probably due to a reduction in the repulsive potential in the dimer ground state from solution to crystal. The triplet excimer energy levels in solution and in single crystals are presented for several symmetrically substituted halogenated benzenes and some qualitative data presented for the distribution of the excitaton energy in the monomer and dimer triplet manifold

Journal ArticleDOI
TL;DR: In this article, the steady state flowing afterglow method was used to investigate the depopulation of the excited mercury states by collisions with hydrogen molecules, and the quenching cross sections were estimated to be q1=6.6 A2 and q0=0.25 A2, respectively.
Abstract: Using the steady state flowing afterglow method, hydrogen molecules in their ground states are introduced into the mercury afterglow plasma in which the dissociative recombination process is predominant, and the depopulation of the excited mercury states by collisions with hydrogen molecules are investigated. The quenching of the radiation emitted from 73S1 or 63D state is explained by assuming that, after the dissociative recombination, the dissociated atom produced in the excited state of which transition probability is smaller than those of 73S1 and 63D states is depopulated by collisions with hydrogen molecules. The resonance state 63P1 and the metastable state 63P0 are also quenched and these quenching cross sections are estimated to be q1=6.6 A2 and q0=0.25 A2, respectively.

Book ChapterDOI
01 Jan 1971
TL;DR: In this article, lifetime studies of the influence of solvent excimer formation on electronic energy transfer from 1,6-dimethylnaphthalene to 9,10-diphenylanthracene in pure liquid and in n-heptane solution are reported.
Abstract: Lifetime studies of the influence of solvent excimer formation on electronic energy transfer from 1,6-dimethylnaphthalene to 9,10-diphenylanthracene in pure liquid and in n-heptane solution are reported. It is found that both monomers and excimers can transfer energy to the solute and that their respective energy transfer rate parameters depend on the solvent concentration. The importance of the various processes that may contribute to non-radiative transfer is discussed.

01 Jun 1971
TL;DR: In this article, a double proton exciplex mechanism was proposed for 9-aminoacridine, where the molecule is both a stronger acid and a stronger base in the excited state.
Abstract: : The 'exciplex' mechanism of radiation emission from a dye affords one means of producing a broad fluorescent spectrum without adding to the absorption spectrum. It relies on a change of equilibrium properties in the excited state compared with those of the ground state, and the fluorescence is not from the same chemical species absorbing the radiation. Such a system may show a considerable displacement of the fluorescence and absorption spectra so that the threshold input power for lasing may be reduced and the range of tuning can be extended. Also, by a careful selection of conditions, emissions from both the dye and the exciplex may appear, thereby permitting an even greater tuning range. Two mechanisms apply: the 'proton exciplex', which relates to changes in conventional acidity and basicity in the excited state; and the 'molecular exciplex', which relates to changes in electron-acceptor and electron-donor properties(i.e., changes in Lewis acidity and basicity). Wide tuning range (blue-violet to yellow-green, 122 nanometers) is reported for 4,8-dimethylumbelliferone. It is proposed that this dye operates by a double proton exciplex mechanism, wherein the molecule is both a stronger acid and a stronger base in the excited state. Peculiarities in the lasing action of 9-aminoacridine are discussed.

Journal ArticleDOI
TL;DR: In this article, the time-dependent probability amplitudes of the quantum states of two interacting atoms are calculated when one atom is initially in an excited p state and the other atom is in an s ground state.
Abstract: General expressions for the time-dependent probability amplitudes of the quantum states of two arbitrary, interacting atoms are calculated when one atom is initially in an excited p state and the other atom is in an s ground state. The lifetimes of the excited states and the line shape of the emitted radiation are obtained as functions of both the atomic separation and the energy difference between the excited states of the two atoms. The emission line shape is shown to be doubly peaked and to agree with the line shape of the radiation scattered by a system of two interacting atoms. The expressions for the lifetimes of the excited states are found to be identical to those obtained for the radiation scattering situation.

Book ChapterDOI
01 Jan 1971
TL;DR: The excimer state is localized if the density of the molecular pairs is small and at low temperature, even if all molecules are able to form excimers, as in the case of pyrene as mentioned in this paper.
Abstract: Energy transfer in organic solids exhibiting excimer fluorescence depends on the density of excimer forming sites and on temperature. The excimer state is localized if the density of the molecular pairs is small—as, for example, in amorphous aromatic polymers—and at low temperature, even if all molecules are able to form excimers, as in the case of pyrene. It is delocalized in pyrene at room temperature.

Book ChapterDOI
01 Jan 1971
TL;DR: In this paper, the authors deduced that as the nuclear conformation of a chromophore becomes more planar and linear, the fluorescence and absorption spectra become more structured, narrower, and longwavelength shifted, the Stokes loss becomes smaller, and the maximum value of the molar extinction coefficient, emax, becomes larger.
Abstract: From empirical spectroscopic data it is deduced that as the nuclear conformation of a chromophore becomes more planar and linear, the fluorescence and absorption spectra become more structured, narrower, and long-wavelength shifted, the Stokes loss becomes smaller, and the maximum value of the molar extinction coefficient, emax, becomes larger. Moreover, compounds planar in both the ground state and first excited state are usually more susceptable to excimer formation and/or concentration quenching than nonplanar compounds. The fluorescence and absorption characteristics of several compounds are presented as examples.