Current Search: Ammonia--Spectra (x)
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Title
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RAMAN SPECTRUM STUDY OF PHASE I AND II OF SOLID AMMONIA (GRANEISEN PARAMETERS).
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Creator
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LUO, RENKANG, Florida Atlantic University
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Abstract/Description
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The Raman spectra of ammonia solid I and II were studied in the lattice and intramolecular region. The study of the internal modes of phase I suggests the presence of disorder in the ordered phase. The lattice modes of phase II are, for the first time, carefully reported as two very broad lines superimposed on an overdamped feature. The results confirm the structure previously determined by neutron scattering and NMR that phase II is a typical disordered phase with space group P6,3/mmc. A...
Show moreThe Raman spectra of ammonia solid I and II were studied in the lattice and intramolecular region. The study of the internal modes of phase I suggests the presence of disorder in the ordered phase. The lattice modes of phase II are, for the first time, carefully reported as two very broad lines superimposed on an overdamped feature. The results confirm the structure previously determined by neutron scattering and NMR that phase II is a typical disordered phase with space group P6,3/mmc. A mode assignment was tentatively made and Gruneisen parameters of the two assumed translational modes calculated. In terms of the Michel-Naudts theory of rotational-translational interactions, phase II is in the slow relaxation regime. A four-band model was used for the intramolecular stretching region.
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Date Issued
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1986
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PURL
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http://purl.flvc.org/fcla/dt/14346
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Subject Headings
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Ammonia--Spectra, Raman spectroscopy
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Format
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Document (PDF)
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Title
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TEMPERATURE AND VOLUME DEPENDENCE OF LATTICE VIBRATIONAL FREQUENCIES FOR SOLID AMMONIA I.
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Creator
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NYE, CHARLES LEE., Florida Atlantic University
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Abstract/Description
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The frequencies of three lattice vibrational nodes of solid ammonia I were measured as functions of temperature and molar volume, via Raman spectroscopy. Calculated Gruneisen parameters of 2.6, 2.4, and 0.8, for modes with frequencies near 108 cm^-1 , 140 cm^-1 and 306 cm^-1 , respectively, identify the first two modes to be translational and the third librational in accordance with previous assignments. The Gruneisen parameter of the libration is lower than expected for purely octopolar...
Show moreThe frequencies of three lattice vibrational nodes of solid ammonia I were measured as functions of temperature and molar volume, via Raman spectroscopy. Calculated Gruneisen parameters of 2.6, 2.4, and 0.8, for modes with frequencies near 108 cm^-1 , 140 cm^-1 and 306 cm^-1 , respectively, identify the first two modes to be translational and the third librational in accordance with previous assignments. The Gruneisen parameter of the libration is lower than expected for purely octopolar electrostatic interactions between molecules. The change in frequency with temperature of all three modes is due to their interaction with the mode near 108 cm^-1. The lifetimes of both translations are determined by their rate of combination with librations near 306 cm^-1 and 313 cm^-1. The lifetime of the libration near 306 cm^-1 depends on its rate of combination with the two translations (108 cm^-1 and 140 cm^-1) and a libration near 440 cm^-1.
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Date Issued
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1985
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PURL
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http://purl.flvc.org/fcla/dt/14251
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Subject Headings
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Ammonia--Analysis, Ammonia--Spectra, Lattice dynamics, Raman spectroscopy
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Format
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Document (PDF)