Raman Spectrum of Rocksalt

Abstract

THE Raman spectrum of rocksalt has been interpreted in two different ways: by Born and Bradburn^1,2 in terms of the Born theory of lattice dynamics and by Krishnan³ as evidence in favour of the Raman theory of crystal vibrations. The Born theory predicts the spectrum as a limited continuum with several maxima, formed by the superposition of various continuous but peaked distributions ; the Raman theory requires essentially nine discrete lines which may be somewhat broadened by thermal motions. Confirmation of both interpretations has been claimed from the same experimental evidence, namely, spectrograms and microphotometer tracings published by Rasetti⁴ and by Krishnan³. The inconclusiveness of the experimental results arises mainly from the lack of intensity measurements. The relationship of the peaks to the underlying continuum, which is the major point of contention, can be determined only by an intensity contour at high dispersion.