The vibration spectra of crystals - Part VI. Sylvine
The nine eigenfrequencies of sylvine are evaluated, and it is shown that the wave-length at which the maximum absorption is exhibited by very thin films is much nearer the tirst than the third of them which is the so-called active oscillation of the potassium against the chlorine atoms. The absorption and reflection data over the whole range of wave-lengths are in general accord with the indications of the theory. The force-constants for sylvine are a little smaller than for rock-salt.