Showing papers by "Elena F. Sheka published in 1980"
TL;DR: In this article, the phonon dispersion curves for the 12 external and the four lowest internal modes in d8-naphthalene (C10D8) have been determined at 6K for the ( xi, 0,0), (0, xi, 0), ( 0, 0, xi ), (1/2, xI, 0) and ( x i, xa, 0) directions by coherent inelastic neutron scattering.
Abstract: The phonon dispersion curves for the 12 external and the four lowest internal modes in d8-naphthalene (C10D8) have been determined at 6K for the ( xi ,0,0), (0, xi ,0), (0,0, xi ), (1/2, xi ,0) and ( xi , xi ,0) directions by coherent inelastic neutron scattering. The results agree very well with optical data. Calculations performed in the harmonic approximation for the rigid-molecule model based on the atom '6-exp' potential were carried out beforehand to produce inelastic structure factors, which turned out to be very useful in the experimental work. This model predicts the qualitative behaviour of the dispersion curves surprisingly well, although some frequencies do differ by 20%. The experimental results show many mode-mixing and anticrossing effects. The present results should serve as a basis for improvements on the model.
63 citations
TL;DR: In this article, the coherent neutron scattering intensities from five phonon modes in naphthalene have been measured at twenty four points in reciprocal space, and a fit to these intensities has been obtained by altering the eigenvectors iteratively.
Abstract: The coherent neutron scattering intensities from five phonon modes in naphthalene have been measured at twenty four points in reciprocal space. These intensities are determined by a set of eigenvectors, and a fit to these intensities has been obtained by altering the eigenvectors iteratively. Significantly the best result has been obtained starting from eigenvectors derived from a model calculation, which were found to be close to the final result. This supports our method of assigning neutron scattering results by a comparison with model calculations.
22 citations
TL;DR: In this article, the structure of phonon side bands in luminescence spectra of local excitons is investigated both theoretically and experimentally, and a gradual transition from a spectrum behavior peculiar for deep impurity centers (with wide phonon sigmoid side band) to that peculiar for low temperature intrinsic lumininescence (the side band becomes split into several bands corresponding to long wave lattice phonons) is investigated depending on the local exciton level depth.
Abstract: The structure of phonon side bands in luminescence spectra of local excitons is investigated both theoretically and experimentally. A gradual transition from a spectrum behaviour peculiar for deep impurity centers (with wide phonon side band) to that peculiar for low temperature intrinsic luminescence (the side band becomes split into several bands corresponding to long wave lattice phonons) is investigated depending on the local exciton level depth. Experimental investigations of deuteronaphthalene solutions are presented.
2 citations