Experimental Demonstration of Matter Waves

Further, it was known from the investigations of Davisson and Germer (1927) that in the reflection of beams of electrons by metals deviations occurred from the result to be expected on classical principles, more electrons being reflected in certain directions than in otln rs, so that at certain angles a sort of selective reflection took place. The conjecture was first propounded by Elsasser (1925) that we have before us here a diffraction effect of electronic waves in the metallic lattic.e, similar to that which occurs in X-ray interference in crystals. The exact investigations which were then imdertaken by Davisson and Germer actually gave interference phenomena in precisely tlie same form as the known Lane interference with X-rays. 

Further experiments by G. P. Thomson, Rupp and others showed that when beams of electrons are made to pass tlirough thin foils (metals, mica), diffraction phenomena are obtained, of the same kind 

These diffraction experiments on whole atoms show that the wave structure is not a property peculiar to beams of electrons, but that there is a general principle in question classical mechanics is replaced by a new warn mechanics. For, in the case of an atom, it is clearly the centroid of all its particles (nucleus and electrons), i.e. an abstract point, which satisfies the same wave laws as the individual free electron. Wave mechanics in its developed form does actually render an account of this. 

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