The emission band spectrum of chlorine—I

Abstract

It has long been known that chlorine, in addition to its atomic line spectrum, can be made to emit both continua and discrete bands, under suitable conditions of excitation. The chief results hitherto obtained are summarized below: other references to work on the band spectrum of chlorine (both in emission and absorption) may be found in Kayser’s “Handbuch der Spektroscopie,” vols. 7 and 8. Measurements of the heads of the visible emission bands have been made by Ota and Uchida,* who have arranged them in three systems. There is, however, serious lack of agreement in the “vibration frequencies” (ω’s) where agreement should exist, and this has led us to remeasure the band heads of the whole system. These measurements have been extended considerably in the directions both of higher and of lower frequency, and the use of an improved technique has enabled us to obtain much more accurate measurements of the band heads. These measurements show definitely that the analysis of Ota and Uchida cannot be accepted, as the discrepancies referred to above are greatly in excess of the experimental error. An example is given below, in which are shown the intervals in the n ' progressions ( n '' = 6 and 5) of Ota and Uchida’s System I.