Phonons and structures of tetracene polymorphs at low temperature and high pressure

Crystals of tetracene have been studied by means of lattice phonon Raman spectroscopy as a function of temperature and pressure. Two different phases (polymorphs I and II) have been obtained, depending on sample preparation and history. Polymorph I is the most frequently grown phase, stable at ambient conditions. A pressure induced phase transition, observed above 1 GPa, leads to polymorph II, which is also obtained at temperatures below 140 K. Polymorph II can also be maintained at ambient conditions. We have calculated the crystallographic structures and phonon frequencies as a function of temperature, starting from the configurations of the energy minima found by exploring the potential energy surface of crystalline tetracene. The spectra calculated for the first and second deepest minima match satisfactorily those measured for polymorphs I and II, respectively. All published x-ray structures, once assigned to the appropriate polymorph, are also reproduced.Comment: 8 pages, 5 figures, RevTeX4, update after referees report

POLARITON AND SURFACE EXCITON-STATE EFFECTS IN THE PHOTODYNAMICS OF ORGANIC MOLECULAR-CRYSTALS

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Study of the cholesterol-GM(3) ganglioside interaction by surface pressure measurements and fluorescence microscopy

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Influence of crystal fields on the quasimetallic reflection spectra of crystals: Optical spectra of polymorphs of a squarylium dye

The reflection and Kramers–Kronig absorption spectra have been obtained from the monoclinic and triclinic polymorphs of a squarylium dye, 2,4-bis(4-diethylamino-2-hydroxy phenyl) cyclobutadienediylium-1,3-diolate. The extremely different optical responses were found to arise from two molecular singlet transitions of essentially long axis polarization. Successful application of a four oscillator molecular exciton–polariton theory required the use of point charge densities rather than point dipoles in an extension of the theory which employed both interactions between the two singlets as well as a frequency dependent lattice damping. An intermolecular charge transfer transition is also assigned. The Journal of Chemical Physics is copyrighted by The American Institute of Physics

Behavior of GM(3) ganglioside in lipid monolayers mimicking rafts or fluid phase in membranes

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Anisotropy in Langmuir-Blodgett films studied by generalized spectroscopic ellipsometry

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PURE ELECTRONIC, VIBRONIC, AND 2-PARTICLE SURFACE EXCITONS ON THE ANTHRACENE CRYSTAL .2. EXPERIMENTAL-STUDY AND ANALYSIS OF THE (0,1) REGION

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ORIENTATIONAL STUDIES OF POLYMERS USING POLARIZATION MODULATION INFRARED LINEAR DICHROISM - EXPERIMENTAL PROCEDURE AND QUANTITATIVE-ANALYSIS

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PURE ELECTRONIC, VIBRONIC, AND 2-PARTICLE SURFACE EXCITONS ON THE ANTHRACENE CRYSTAL .1. GENERAL THEORETICAL BASIS, EXPERIMENTAL-STUDY, AND ANALYSIS OF THE (0,0) REGION

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