Extension of the Visible Absorption System of NO₂ to Longer Wave-Lengths

Abstract

IN two recent letters to NATURE, Cassie and Bailey¹ as well as Harris, Benedict and King² report new investigations of the infra-red and ultra-violet absorption spectrum of NO₂. We should like to remark that we have recently made new investigations of the visible absorption system of NO₂ which, as is well known, is extremely complicated. In consequence of this, neither its vibrational nor rotational structure has as yet been analysed. A possible explanation for this complicated structure is that, in consequence of the Franck-Condon principle, chiefly the higher vibrational levels in the upper state are excited.