Model
Digital Document
Publisher
Florida Atlantic University
Description
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
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.
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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