Translational Frequencies of Molecules in Naphthalene, Durene, and Anthracene Single Crystals at Low Temperatures

Hadni, A.; Wyncke, B.; Morlot, G.; Gerbaux, X.

doi:10.1063/1.1672541

Cited by 41 publications

(11 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…(3) The situation represents independent librational motions of each molecular partner in its own sublattice. This describes our sublattice limit where the phonon bands of the two sublattices will be observed at different frequencies.…”

Section: Theoretical Discussion Using a Simple Modelmentioning

confidence: 99%

Intermolecular vibrations of a crystalline molecular complex

Chen

Prasad

1977

The Journal of Chemical Physics

View full text Add to dashboard Cite

Comment on: Structures, stabilities, and intermolecular vibrational frequencies of small ammonia complexes by molecular mechanics for clusters analysis J. Chem. Phys. 95, 3861 (1991); 10.1063/1.460792Structures, stabilities, and intermolecular vibrational frequencies of small ammonia complexes by molecular mechanics for clusters analysisThe nature of intermolecular vibrations in a crystalline molecular complex is examined using a simple model of a crystal with one molecule of a 1:1 complex per unit cell. It is shown that two limiting descriptions can result depending on the coupling strength between molecular components in the complex: (i) The giant molecule limit describes the case of a strong coupling where the intermolecular motions are the motions of the complex as one entity. (ii) The sublattice limit is applicable in the weak coupling case. Here, the motion can be characterized as an intermolecular motion belonging to the sublattice of the individual components. The phonon bands of naphthalene:octafluoronaphthalene crystals are examined within the framework of the simple model. The results predict phonons to be close to the sublattice limit. Our experimental study of Raman phonon spectra using isotopic mixed crystals of the complex is in agreement' with the theoretical predictions and show that the low frequency phonons belong predominantly to the CJOFg sublattice, while the high frequency phonons characterize the CJOHg sublattice motions.

show abstract

Section: Theoretical Discussion Using a Simple Modelmentioning

confidence: 99%

Intermolecular vibrations of a crystalline molecular complex

Chen

Prasad

1977

The Journal of Chemical Physics

View full text Add to dashboard Cite

show abstract

“…This broadening is not a result of mixing with translational phonons, as the highest translational phonon frequency is only about 105 cm-I (at liquid nitrogen temperature). 31 The broadening can be partially explained by a calculation based on a moment expansion at the amalgamation limit. 28 According to the result of this calculation, the broadening of different modes in a mixed crystal of fixed composition is proportional to the trap depth and the broadening is largest in a 50% mixture.…”

Section: Methodsmentioning

confidence: 99%

Raman Phonon Spectra of Isotopic Mixed Naphthalene Crystals: Librational Exciton Model and the Amalgamation Limit

Prasad

Kopelman

1972

The Journal of Chemical Physics

View full text Add to dashboard Cite

We present an experimental Raman study of lattice modes in neat and mixed (10%–90%) crystals of naphthalene-h8 and naphthalene-d8 at 100°K with 1 cm−1 resolution. The spectral features of the neat crystals are preserved in the heavily doped mixed crystals, with small shifts and broadenings characteristic of an amalgamation limit that assumes weakly coupled excitation bands in the restricted Frenkel-Davydov limit. Rotation-translation interaction does not affect the mixed crystal spectra, thus making the Raman technique uniquely suited for the investigation of the librational (rotational) phonon band structure. The evidence is against localized or pseudolocalized phonons in these isotopic mixed crystals.

show abstract

“…Using data for naphthalene [29] (a = 8"235~, b= 6"003A, c= 8"658A, 7 = 122"7~ we have V 0 = 360"2.~ 3. ~ is derived from data given in [-30], and we get ~ = 1"2 x 10 a ms -l. The maximum frequency then becomes ~0,, = 9'5 x 1012s-1 and the corresponding Debye temperature 0,r = 72"6 K. Experimental data for the frequencies of the optical phonons are taken from [31][32][33][34][35]. Because these frequencies are temperature dependent it is not possible to derive one exact value for all temperatures.…”

Section: Parameters Of the Modelmentioning

confidence: 99%

Model calculation of the temperature dependence of triplet exciton E.S.R. line shapes for local exciton phonon interaction

Winkler

Reineker

1987

Molecular Physics

View full text Add to dashboard Cite

The E.S.R. line shape of a triplet exciton moving in a coupled coherent and incoherent manner within a pair of differently oriented molecules is calculated. The hamiltonian describing the model includes the excitation energies of the identical, but differently oriented molecules, the interaction matrix element describing the coherent exciton transfer, the Zeeman energy, and the fine-structure terms of the molecules. Furthermore it contains the phonons which are treated quantum mechanically and their linear and local interaction with the exciton. Using a unitary transformation of the hamiltonian, the exciton-phonon interaction is transformed into a phonon modulated exciton transfer operator. Considering now the phonons a heat bath, with the help of the transformed hamiltonian the Liouville equation for the reduced density operator is derived, which contains only triplet exciton degrees of freedom. "['he eigenvalues and eigenvectors of the reduced density matrix are calculated numerically using parameters characteristic for naphthalene. From linear response theory the E.S.R. line shape is determined using the eigensolutions of the Liouville equation. These calculations show that in the high temperature limit a localization of the exciton either at molecule A or molecule B occurs for all values of the exciton-phonon interaction. The E.S.R. line shape is also discussed in regions where level anticrossings occur.

show abstract

Translational Frequencies of Molecules in Naphthalene, Durene, and Anthracene Single Crystals at Low Temperatures

Cited by 41 publications

References 3 publications

Intermolecular vibrations of a crystalline molecular complex

Intermolecular vibrations of a crystalline molecular complex

Raman Phonon Spectra of Isotopic Mixed Naphthalene Crystals: Librational Exciton Model and the Amalgamation Limit

Model calculation of the temperature dependence of triplet exciton E.S.R. line shapes for local exciton phonon interaction

Contact Info

Product

Resources

About