Étude des spectres de l'exciton aux très basses températures

Abstract
An account is given on the résults obtained in the author's laboratory on the absorption spectra of a number of crystals at very low temperatures. In most cases it has been found that the absorption spectra give evidence of narrow line structure. The breadth of some of these lines does not exceed one Å or even less. Sometimes they form hydrogen like series which are in several compourids accompanied by vibration satellites. In anisotropic crystals the absorption lines are dichroic. These results are believed to give an experimental evidence for the existence of excitons.