The absorption band spectrum of chlorine

Abstract

The familiar yellow-green colour of chlorine is due to a broad region of absorption in the violet and blue regions of the spectrum. This absorption is continuous, i. e ., it shows no sign of structure under high resolving power, and extends from about 2300 A. U. towards the direction of lower frequency, becoming exceedingly feeble in the neighbourhood of 5000 A. U. The maximum of absorption lies at 3300 A. U. In addition to this continuous absorption, a feeble band absorption exists in the region 4785-6220 A. U. approximately, part of which is overlapped by the continuous absorption. The absorption band spectrum of chlorine has been studied by several workers, the first accurate measurements having been made by Laird, who measured the wave-lengths of some thousands of lines, but did not make any analysis. More recently Kuhn and Nakamura have measured the wave-lengths and frequencies of the heads of the bands, and have arranged them into five progressions, each having a common vibrational quantum number in the lower state (the initial state in absorption).