Fluorescence Spectra Of Anthracene Research Articles

Generating Function Approach to Single Vibronic Level Fluorescence Spectra.

An efficient time-dependent generating function method to compute vibronic emission and absorption spectra arising from transitions from a singly excited vibrational initial state is presented. In contrast to existing finite temperature approaches that intrinsically contain these transitions weighted by a Boltzmann factor, the current approach allows one to calculate these transitions individually. Using vibrational frequencies and normal modes computed by the second-order approximate coupled cluster (CC2) method, this formalism is used to compute the single vibronic level (SVL) fluorescence spectra of anthracene. Calculated spectra are in excellent agreement with spectra measured in jet-cooled expansion experiments. Duschinsky mixing is necessary to explain intensities of certain peaks. In a few cases, CC2, however, underestimates Duschinsky mixing, leading to too low peak intensities. An empirical correction of the Duschinsky matrix is presented. The presented method has the potential to facilitate the assignment and interpretation of SVL fluorescence spectra.

ChemInform Abstract: Experimental Determination of the S1 Torsional Potential of 9,9′- Bianthryl in 2-Methyl-butane by Simultaneous Franck-Condon and Band Shape Analysis of Temperature Dependent Optical Fluorescence Spectra.

Optical fluorescence spectra of anthracene (AN) and of 9,9’‐bianthryl (BA) have been measured in the apolar solvent 2‐methyl‐butane (2MB) at seven different temperatures in the range 123 K to 298 K. The AN spectra are strongly structured and consist of simple Franck–Condon (FC) progressions. The BA spectra on the other hand are broad and show unusual temperature dependencies. These effects are interpreted within a two state model with five vibrational and one torsional degree of freedom. A FC analysis is carried out using vibronic band shape functions which are convolutions of two functions. The first one is a Gaussian representing the spectral broadening due to librations and intermolecular interactions. The second one results from a semiclassical treatment of the intramolecular torsional mode (large amplitude motion, LAM). Optical transitions are assumed to occur from ensembles which are thermally equilibrated with respect to their nuclear degrees of freedom. The Boltzmann distribution with respect to the LAM potentials in combination with a change of the transition frequency as a function of the torsional angle φ is identified as the predominant broadening mechanism. The LAM potentials in the S0 and S1 state are represented by a three parameter cosine series. A nonlinear least‐squares fit of the experimental spectra leads to a single consistent set of model parameters valid for all temperatures. The S1 double minimum LAM potential of BA in 2MB is found to have minima at φeq=62° (and 118°) and a local barrier at φ=90° of 255 cm−1.

Raman scattering tensor elements for some ag modes of anthracene

AbstractThe intensities of the Raman lines of anthracene in solution and in the pure crystal at room temperature have been measured using several excitation frequencies (ν0) in the pre‐resonance region. The data were used to derive molecular scattering elements αii at each νo for a number of ag fundamentals. While the values of αxx and αyy are constant over the restricted range of excitation used, αzz shows an enhancement as νo moves towards resonance with the first absorption system (I). Overlap factors were determined from the fluorescence spectrum of anthracene in a biphenyl matrix, and these values were used to calculate the contribution αzz(I) due to scattering off the first excited electronic state. Working beyond the oriented‐gas assumption improved the fit between calculated and observed enhancement. There is a measurable background contribution to αzz due to scattering off higher excited states and this has an opposite algebraic sign from αzz(I) for all ag fundamentals except possibly for the 394 cm−1 mode.

Spectral shifts in the fluorescence spectrum of anthracene under the influence of laser driven shock compression

We report spectral shifts in the fluorescence emission of a solution of anthracene in benzene under the influence of laser driven shock compression. Red-shifts of up to 800 cm −1 are observed in the peak of the 0–1 vibronic band of anthracene corresponding to maximum pressures of =10 kbar. These results are in agreement with literature values of spectral shifts obtained under conditions of high static pressure. Laser driven shock provides an attractive alternative to conventional shock generation schemes when used in conjunction with optical spectroscopy as a probe of molecular level changes.

Temperature and solvent influence on the fluorescence spectrum of anthracene and anthracene-diethylaniline exciplex

By studying the modifications of the fluorescence and excitation bands of anthracene (A) both under the influence of the solvent and temperature, we concluded that these changes are due to the different contributions, both to emission and absorption, of certain molecular species, which appear by the deformation of the anthracene molecule. The influence of solvent and temperature upon the frequency of the maximum of emission of the exciplex anthracene-diethylaniline (DEA) can be explained by the fact that the A molecular species which are connected to the molecules of DEA are changed under the influence of the temperature and solvent.

Fluorescence spectra of anthracene and tetracene crystals corrected for spatial distribution of excitons

The fluorescence spectra of anthracene and tetracene single crystals have been measured with the application of a special procedure for correction for reabsorption and to independently determine the spatial distribution of excitons. The corrected spectra show the short-wavelength fluorescence maximum to be blue shifted and over an order of magnitude greater than those for the remaining emission bands.

A Further Evidence of the Vibronic Coupling through b3g Vibrational Modes in the Fluorescence Spectrum of Anthracene

Abstract Angular dependence of the fluorescence polarization spectra of anthracene was investigated in polyethylene films using a sample rotation technique. An important role of a nontotally symmetric vibration, the b3g ring vibration at 1655 cm−1, was further confirmed by a combination of this technique and the modulation polarization technique developed previously.

A Development in Polarization Experiments; Emission Spectra of Anthracene, Dibenzothiophene, and Xanthone in Stretched Polyethylene Films

Abstract The polarized emission spectra of anthracene, dibenzothiophene, and xanthone have been studied in stretched polyethylene films at 77 and 4.2 K. Applicability and advantage of this method are examined by virtue of conventional polarization technique and modulation technique. The latter leads us to finding of an important role of a nontotally symmetric vibration, the b3g ring vibration at 1655 cm−1, in the fluorescence spectrum of anthracene. An assignment for several prominent vibrational bands in the phosphorescence spectrum of dibenzothiophene is proposed from detailed analysis of the modulation polarization spectrum at 77 K. The phosphorescence properties of xanthone are also investigated.

Die Schwingungsstruktur der Shpolskii-Spektren von Anthracen, 9-Methyl-und 9,10-Dimethylanthracen in n-Hexan bei 77 K. I. Fluoreszenz / The Vibronic Structure of Shpolskii Spectra of Anthracene, 9-Methyl- and 9,10-Dimethylanthracene in n-Hexane at 77 K I. Fluorescene

Abstract The fluorescence spectra of anthracene, 9-methyl- and 9,10-dimethylanthracene in n-hexane at 77 K were measured. The Franck-Condon-Factors are evaluated using equilibrium geometries, vibrational frequencies and normal coordinates of the molecules in the ground and first excited singlet state which were calculated by the QCFF/PI-method. These results are then compared with experimentally determined frequencies and estimated intensities. The new vibronic lines in the fluorescence spectra of the methylated anthracenes correspond to totally symmetric vibrations, up to 1000 cm-1 originated mostly by mixing with out-of-plane vibrations of the atoms of the anthracene skeleton. Above 1000 cm-1 these vibrations which have greater projections of their normal coordinates on the internal coordinates of the methyl groups, are not visible as vibronic lines in the fluorescence spectra. The multiplet structures of the O-O-transitions are ascertained.

Fluorescence spectra of anthracene and pyrene in water and in aqueous surfactant solution

The fluorescence and excitation spectra of anthracene and pyrene have been measured in water and in aqueous solution of sodium dodecyl sulfate (SDS), and compared with the spectra in ethanol, for microcrystals and in a solution by the dilution method. The molecular spectra observed in water exhibit large broadenings and red-shifts due to the specific solvent effects of water. In aqueous SDS solution the spectra of anthracene are considerably broadened and red-shifted, suggesting the existence of the molecules near the micellar surface, while in the emission spectrum of pyrene remarkable intensity reductions of the vibronic bands have been observed, indicating a weak polarity of the environment in the SDS micelles.

Electronic Absorption and Fluorescence Spectra of Anthracene, [D10]-Anthracene, and Acridine in n-Alkane Matrices at 4°K

A systematic examination has been made of the electronic absorption and fluorescence spectra of anthracene and [D10]-anthracene in n-hexane, n-heptane, and n-octane matrices at 4°K. Vibrational analyses have been made and the correspondence between most of the modes of the two molecules has been established. A number of errors in previously published anthracene data are pointed out. The existence, in the fluorescence spectrum of anthracene in n-heptane at 4°K, of a line which lies 391 cm−1 above the electronic origin has been shown to be part of the environment multiplet structure characteristic of these matrix spectra. It is clear that the line has no connection with the intense 390-cm−1 vibrational frequency since its position with respect to the main origin is the same in the spectrum of [D10]-anthracene, for which the vibrational frequency is 376 cm−1. A possible hypothesis that fluorescence was occurring from vibrationally excited molecules is therefore ruled out. The distinction between (a) “environment multiplets” for molecules in different crystal environments and (b) spectral components deriving from local lattice vibrations is stressed. The environment multiplet structure of the undeuterated and deuterated molecules are found to be virtually identical. The 4°K spectrum of acridine in n-heptane shows some weak sharp lines on broad background of absorption. The line shapes of the 77°K anthracene and 4°K acridine spectra are discussed in terms of the relative half-widths and intensities of components representing no-phonon and phonon transitions, respectively.

Fluorescence Spectra of Anthracene and Naphthalene Excited by Giant-Pulse Ruby Laser

The fluorescence spectra of anthracene and naphthalene in the visible region, when excited by a giant-pulse ruby laser, were recorded. The spectrum of anthracene consisted of four very broad bands extending from blue to violet. In the case of naphthalene, the spectrum consisted of comparably much sharper bands extending from blue to deep violet. Two-photon excitation from vibrationally excited levels of the ground electronic state is believed to be the process involved in producing the fluorescence in naphthalene.

Spectral Shifts and Broadening of the Fluorescence of Anthracene and Tetracene in Several Host Crystals at High Pressures

The fluorescence spectra of anthracene in biphenyl, p-terphenyl, naphthalene, and phenanthrene and those of tetracene in p-terphenyl, naphthalene, phenanthrene, and anthracene were measured at pressures as great as 50 kbar. The pressure effects on the spectra of the guests are generally analogous to the pressure effects in solution or the gas phase. Due to the increased dispersion interaction between these nonpolar molecules upon compression, the energies of the electronic transitions are shifted toward the red (lower energy), and the spectral bands are broadened, while the integrated intensity remains approximately constant. As the pressure is released, the fluorescence spectra return to those obtained before compression. The spectral shifts with pressure are satisfactorily interpreted in terms of a second-order perturbation theory using a dipole–dipole approximation. For three of the eight guest–host combinations, the fluorescence spectra above 35 kbar were considerably broader than expected. The similar broadening observed for the pure host crystals suggests that mixed excimers are produced at high pressures. On the basis of the present data, however, it is not possible to give an unambiguous explanation of the extensive broadening.

The Effect of Pressure on the Fluorescence Spectra of Anthracene, Chrysene and Pyrene

The Effect of Pressure on the Fluorescence Spectra of Anthracene, Chrysene and Pyrene

Absorption and fluorescence of anthracene

The absorption and fluorescence spectra of anthracene in n-heptane, fluorene, and biphenyl matrices have been measured at 4°K. Both in the ground and 1 B 1 u excited electronic states, eight a g and three b 3 g fundamentals have been assigned. Other possible fundamentals, including some nontotally symmetric modes allowed to appear by crystal forces, are indicated. Anharmonicity was detected only by the appearance of a number of examples of Fermi resonance between vibrational modes both in absorption and in fluorescence. No evidence for a second weak electronic transition was found.

Electronic and Vibrational States of Anthracene

The polarized absorption and fluorescence spectra of anthracene have been measured in dilute solid solution in single crystals of naphthalene and phenanthrene at 20°K. The lowest singlet-singlet transition is proven to be polarized along the short molecular axis, and hence 1B2u—1Ag(1La—1A), in agreement with theoretical predictions. Vibrational frequencies are compared in the ground state and in the first excited state. The polarization of the fluorescence of anthracene in phenanthrene has also been studied as a function of temperature. The fluorescence is partially polarized at 300°K, but is depolarized at 20°K.