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Showing papers on "Excimer published in 1973"





Journal ArticleDOI
TL;DR: In this paper, the possibilities of ground state complex and excimer formation in various liquid solvents were examined thoroughly, and the results of the self-complexion of p-(N,N-dimethylamino)-benzonitrile and its hetero-complex formation with benzonitriles in cyclohexane matrix were studied in detail.
Abstract: Electrostatic self-complex formation of p-(N,N-dimethylamino)-benzonitrile and its hetero-complex formation with benzonitrile in cyclohexane matrix were studied in detail. The possibilities of ground state complex and excimer formation in various liquid solvents were examined thoroughly.

52 citations



Journal ArticleDOI
TL;DR: In this article, the fluorescence spectra of N, N-dialkyl-p -cyanoanilines in fluid media have been re-examined.

40 citations



Journal ArticleDOI
TL;DR: In this paper, a detailed study of the absorption spectra, fluorescence spectra and fluorescence lifetimes of symmetric dimers of anthracene and 9-substituted anthracenes was made.
Abstract: Sandwich dimers are obtained by photochemical cleavage of dianthracene and related compounds in a rigid glass matrix at 77 K. Detailed studies of the absorption spectra, fluorescence spectra, and fluorescence lifetimes of symmetric dimers of anthracene and 9-substituted anthracenes (both molecules the same) and dissimilar dimers (one molecule anthracene, the other 9- or 9,10-substituted anthracene) have been made. Particular attention has been paid to these properties during dissociation of the dimers as the glass is allowed to soften. The fluorescence properties show a discontinuity during this dissociation. The excimer emission maxima (lifetimes about 200 ns) move a little to higher energy (lifetimes decrease to about 100 ns) then broad structure is observed in the spectra and lifetimes drop to about 5 ns. The fluorescence spectra of the dissimilar dimers are of the excimer type with lifetimes of about 100 ns. These values do not appear to be compatible with existing theories of the excimer state.

32 citations


Journal ArticleDOI
TL;DR: In this article, it was shown that the only model which predicts the observed time resolved spectroscopy results requires a long range resonant interaction strength much greater than that obtained theoretically.

26 citations


ReportDOI
28 Sep 1973
TL;DR: In this paper, a model of the excimer formation and decay processes in electron beam pumped high density rare gases has been developed, and the model has been compared with recent measurements of the Xe and information about the radiative lifetimes and dominant collision mechanisms are obtained.
Abstract: : A model of the excimer formation and decay processes in electron beam pumped high density rare gases has been developed. The model has been compared with recent measurements of the excimer formation and decay rates in Xe and information about the radiative lifetimes and dominant collision mechanisms are obtained. Several important conclusions that have bearing on the vuv laser characteristics of these systems are discussed.

24 citations


Journal ArticleDOI
TL;DR: In this article, the blue monomer fluorescence of perylene in cyclohexane was replaced by an orange excimer fluorescence emission upon freezing the solution with increasing pressure, and the temperature dependence of the excimer decay was characterized by a radiative lifetime of 80 nsec and an activation energy of 670 cm −1.

Journal ArticleDOI
TL;DR: In this paper, a technique based on the optic-acoustic effect has been used to measure the triplet state lifetime of benzene over a range of pressure, and the collisional efficiency was discussed in terms of triplet excimer formation.


Journal ArticleDOI
TL;DR: In this paper, the authors measured the molecular continuum radiation from Hg2* in the 4000-5000 A range; the excitation was produced by a high energy, short pulse electron beam.

Journal ArticleDOI
TL;DR: In this article, the excimer fluorescence from the dinucleotide CpC has been observed to be strikingly different from that of the monomer and the mixed polarization in the absorption reflects significant ground state interaction.

Journal ArticleDOI
TL;DR: In this article, absorption and fluorescence spectroscopy of acridine orange and 9-aminoacridine with poly-A and DNA was studied by means of circular dichroism and circular polarization of fluorescence, and the spectral properties of the dye in AO:DNA complexes were different at the P/D ratios of 15 and 3, reflecting different modes of complexing.
Abstract: Complexes of acridine orange (AO) and 9-aminoacridine (9-AA) with poly-A and DNA were studied by absorption and fluorescence spectroscopy, circular dichroism and circular polarization of fluorescence. The nucleotide:dye ratio (P/D) ranged from 20–2. The dye in the AO:poly-A complex is predominantly in the dimeric form. The optical activity of the monomer dye in the excited state is very small, while that of the dimeric dye is relatively large and its dependence on wavelength and P/D indicates the presence of higher aggregates. At low P/D ratios some transfer of electronic excitation energy from dimer to monomer takes place. The spectral properties of the dye in AO:DNA complexes are different at the P/D ratios of 15 and 3, reflecting different modes of complexing. In contrast to the AO:poly-A complexes, the optical activity of the AO:DNA complexes in the ground and in the excited states are of comparable magnitude; little change thus seems to take place in the interaction between dye and polymer upon electronic excitation of the dye in AO:DNA. In the 9-AA:poly-A complex the dye does not tend to dimerize when in the ground state. Excimer emission was, however, observed; dimers and higher aggregates of high optical activity form upon electronic excitation. In the complex of proflavine:DNA, the bound dye shows appreciable optical activity when in the ground state but is optically inactive when in the excited state. The mode of interaction between this dye and DNA thus changes appreciably upon electronic excitation. The occurrence of two electronic transitions in the last absorption band of acridine dyes and its implication on the interpretation of the corresponding CD spectra is discussed.

Journal ArticleDOI
TL;DR: In this paper, the authors report the observance of quinoline and isoquinoline excimer fluorescence in liquid ethanol solutions, in the absence of quenching by an impurity molecule, the following kinetic scheme describes the interaction of an electronically excited molecule with a similar molecule in the ground state: In scheme ( 1 ) M, M* and D* refer to unexcited monomer, excited monomer and excimer, respectively.
Abstract: INTRODUCTION Excimer and/or exciplex formation has been increasingly implicated in photobiological aad photochemical studies. Although excimer formation has been shown to be a rather general process involving photoexcited aromatic molecules (Birks, 1970), much less spectroscopic data is available concerning excimer formation in heterocyclic molecules. The principal barrier, in general, has been the weak luminescence from heterocyclic molecules, particularly n-heterocyclics, effected by the low oscillator strengths of the low lying, n,n* transitions. In the quinoline and isoquinoline molecules, however, the n,n* electronic state is lowest (although the lowest n,n* and n,r* states are almost degenerate in quinoline (El-Sayed and Kasha. 1959; Coppens et al., 1962; Lim and Yu, 1967). As a result, fluorescence from both these molecules is enhanced in a polar solvent (El-Sayed, 1963). This enhancement may be understood from a reduction in the n,n* and r,r* vibrational coupling due to a raising of the n,n* state and a lowering of the r,n* state in a polar medium (Becker, 1969) and raises the question of the effectiveness of excimer formation under these conditions. I n this note we report the observance of quinoline and isoquinoline excimer fluorescence in liquid ethanol solutions. In the absence of quenching by an impurity molecule, the following kinetic scheme describes the interaction of an electronically excited molecule with a similar molecule in the ground state: In scheme ( 1 ) M , M* and D* refer to unexcited monomer, excited monomer and excimer, respectively. The rate constants k D M , kMD, klM, klD, k f M , kfD, ISM and kIsD are for excimer formation, excimer dissociation, internal conversion of the monomer, internal conversion of the excimer, monomer fluorescence, excimer fluorescence, intersystem crossing for the monomer and intersystem crossing for the excimer, respectively. The energy of the monomer fluorescence emission is huh(, and the energy of the excimer fluorescence emission is hvD. Under photostationary conditions, we have (Birks, 1970):

Journal ArticleDOI
TL;DR: In this article, the fluorescence of pyrene has been studied as a function of pressure, concentration and temperature in the solvents ethanol and cyclohexane and the spectra and lifetime of both monomeric pyrene and the excited state complex were characterized at different pressures.
Abstract: The fluorescence of pyrene has been studied as a function of pressure, concentration and temperature in the solvents ethanol and cyclohexane. The spectra and lifetime of both monomeric pyrene and the excited state complex are characterized at different pressures. Compression of ethanol shifts the monomer‐excimer equilibrium towards the monomer, while compression of cyclohexane leads to aggregation and pyrene excimer fluorescence over a large concentration range.

Journal ArticleDOI
TL;DR: In this paper, an emission at shorter wavelength than the excimer emission band at room temperature was found to originate from the intrinsic monomer structure in the crystal surface, and the transfer probabilities of the excitation energies corresponding to the new emission at low temperature and the emission at short wavelength more similar to that of excimer to doped perylene molecules were observed by a pulsed method and their temperature dependences were obtained.
Abstract: A new emission different from the usual excimer emission in pyrene crystal was found at low temperature. Also, an emission at shorter wavelength than the excimer emission band at room temperature was found to originate from the intrinsic monomer structure in the crystal surface. Furthermore, the transfer probabilities of the excitation energies corresponding to the new emission at low temperature and the emission at shorter wavelength than the excimer emission at room temperature to doped perylene molecules were observed by a pulsed method and their temperature dependences were obtained. By the analysis of these results the diffusion coefficient D of the migration of the excitation energy of the former emission was obtained as D = D 0 exp (- E / k T ) ( D 0 =1.5×10 -4 cm 2 sec -1 and E =0.003 eV). On the other hand, the diffusion coefficient D of the excitation energy of the latter emission was given by D =3.6×10 -4 T -1/2 .

Journal ArticleDOI
TL;DR: In this article, the e.c.l. of pyrene in acetonitrile has been studied using a controlledpotential double-step method, and the following results were obtained: (1) the electrode potential regions where the emission was observed were in agreement with those of cation and anion formation; (2) the spectrum had two main bands at 400 nm and 470 nm and a subsidiary band at the longer wavelength.

Journal ArticleDOI
TL;DR: In this article, a well resolved spectrum was obtained for the pyrene excimer in deoxygenated cyclohexane using modulation excitation spectrophotometry, where the excimer was defined as a pyrene derivative.

Journal ArticleDOI
TL;DR: In this paper, evidence for the formation of an intramolecular triplet excimer in the case of 1,3-diphenylpropane during the softening of the isopentane degassed glass matrix was presented.

28 Sep 1973
TL;DR: In this paper, a model of the excimer formation and decay processes in electron beam pumped high density rare gases has been developed, which has been compared with recent measurements of the Xe and information about the radiative lifetimes and dominant collision mechanisms are obtained.
Abstract: Abstract : A model of the excimer formation and decay processes in electron beam pumped high density rare gases has been developed. The model has been compared with recent measurements of the excimer formation and decay rates in Xe and information about the radiative lifetimes and dominant collision mechanisms are obtained. Several important conclusions that have bearing on the vuv laser characteristics of these systems are discussed.


Journal ArticleDOI
TL;DR: In this paper, the degradation of monomer and excimer fluorescence is studied with irradiation by uv light, and the effects of surface treatment, ambient gas and the residual monomer are examined.
Abstract: Degradation of monomer and excimer fluorescence is studied with irradiation by uv light. Effects of surface treatment, ambient gas and the residual monomer are examined. It is found that the degradation is accelerated by the residual monomer and oxygen. Expressions for the degradation curve are derived taking direct damage, filter effect and quenching into consideration. From the comparison of these expressions with experiments, quenching is most important for the observed fluorescence degradation. For small irradiation doses and small concentrations of the residual monomer, the degradation obeys the Stern-Volmer type equation in both monomer and excimer fluorescence. The fluorescence and absorption spectra of the samples are also observed at various irradiation doses.

Journal ArticleDOI
01 Apr 1973-Nature
TL;DR: The explanation of muscle contraction by McClare is at variance with the current tenets of molecular spectroscopy, and lifetime measurements have shown that the excimer has a shorter half-life than that of the parent monomer.
Abstract: THE explanation of muscle contraction by McClare1,2 is at variance with the current tenets of molecular spectroscopy. Lifetime measurements have shown that, in most cases, the excimer has a shorter half-life than that of the parent monomer3. In pyrene, the example quoted by McClare, the half-life (at room temperature) of the monomer is 31 × 10−8 s, while that of the excimer is only 4.4 × 10−8 s.

Journal ArticleDOI
19 Oct 1973-Nature
TL;DR: It is suggested that the energy of the bond vibration produced on ATP hydrolysis is less than that of the excited state of an isolated oscillator, so that only when the two oscillators are close enough to perturb each other sufficiently do they resonate with the bond vibrations and then become excited.
Abstract: THE fundamental idea in a highly speculative new kind of muscle model1 was that a bond vibration is first produced by an exothermic chemical reaction, the energy is transferred resonantly to an electronic excited state of identical frequency, then trapped in an excimer state formed between two such electronic oscillators and finally converted into external work as the two oscillators approach each other. The first part of Naqvi's criticism2 was that the experiment I quoted as an example of energy trapping in excimers was mistaken. This I concede; clearly the pyrene experiments can no longer be used to show that excimer fluorescence is dipole-forbidden. The accepted theory clearly predicts, however, that, in special conditions, the excimer state may yet be long lived. In its longer version3 my muscle model already has a design feature which enables Naqvi's criticism to be overcome. If the oscillator was indeed first excited to a singlet state and only later diffused into interaction distance with another oscillator in the ground state then, as Naqvi argues, the triplet state would be at a lower energy and decay into it would be difficult to avoid. My suggestion3 was, however, that the energy of the bond vibration produced on ATP hydrolysis is less than that of the excited state of an isolated oscillator, so that only when the two oscillators are close enough to perturb each other sufficiently do they resonate with the bond vibration and then become excited. This feature was introduced, first, to protect the postulated bond vibration (by allowing it to be buried in a protein and yet to interact with the environment in this way) and, second, to ensure that only the anti-symmetric attractive excimer state is produced on excitation. I now suggest a third function: to ensure that the excimer only becomes excited when its energy is already below that of the triplet state. In this case decay into the triplet state would be prevented, and the fluorescence would become fully dipole-forbidden.

Journal ArticleDOI
TL;DR: In this article, the fluorescence of pyrene has been studied as a function of pressure, concentration and temperature in the solvents ethanol and cyclohexane and the spectra and lifetime of both monomeric pyrene and the excited state complex were characterized at different pressures.
Abstract: The fluorescence of pyrene has been studied as a function of pressure, concentration and temperature in the solvents ethanol and cyclohexane. The spectra and lifetime of both monomeric pyrene and the excited state complex are characterized at different pressures. Compression of ethanol shifts the monomer‐excimer equilibrium towards the monomer, while compression of cyclohexane leads to aggregation and pyrene excimer fluorescence over a large concentration range.