| dc.description.abstract | The recent development of interferometers operating in the
far-infrared frequency region, coupled with the use of modern
high-speed digital computers for processing the interferometric
data, has made this frequency region more readily available for
investigation. It became apparent quite early that most, if not
all, compounds exhibit absorptions in this region, confirming the
speculations of earlier dielectrics studies. For polar molecules,
the existence of these absorptions has been attributed to a variety
of causes, several of which have in common a concept of a
short-lived pseudo-lattice or cage of molecules surrounding a
central trapped molecule which could absorb energy from an applied
oscillating electromagnetic field in order to move within the potential
energy well created by the cage members.
In the present work, an attempt has been made to examine this
concept by varying the temperature of the sample, with a view to
altering the size and rigidity of the cage. The type of motion
exhibited by the central molecule has also been considered.
In general, both the intensity and frequency of maximum absorption
increased smoothly with decreased temperature within the
liquid phase, and within certain solid phases in which molecular
rotational motion was allowed. On passing into non-rotator solid
phases, however, the broad, featureless absorption curve of the
liquid was replaced abruptly by one containing several sharp, narrow and intense absorption peaks.
It has been suggested that the broad absorption bands of the
liquid phase are composed of several overlapping bands due to different
types of molecular motion. Further, each of the component
bands was suggested to arise from the differences between the
kinetic energy possessed by a central molecule, and the energy
barrier created by the molecular cage. The kinetic energy of the
central molecule was suggested to be governed by a continuous distribution.
Similarly, the energy barrier might also be governed
by a second continuous distribution. | |
