On the fluorescence of iodine vapour excited by ultra-violet light

Abstract

In a recent communication by the writer a new fluorescence spectrum of iodine vapour was described which could be stimulated by the light from the mercury arc. This fluorescence spectrum consisted of a set of narrow bands extending from λ 4600 down to λ 2100. While of this spectrum was clearly defined, the most intensely marked portion of it was made up of a set of seven equally spaced bands between λ 3315 and λ 3175. in obtaining the spectrum a highly exhausted tube of fused quartz containing a few iodine crystals was inserted axially in an ordinary glass Cooper-Hewitt mercury are lamp, with a lateral anode and provided with a short extension at the positive end, to which the quartz tube was sealed with mastic wax. The quartz iodine vapour tube was provided with a window of clear fused quartz, towards which the collimator of quartz spectrograph was directed in taking the photographs. When the Copper-Hewitt tube was in action the are played directly upon the inserted quartz tube and so subjected the vapour contained in it to intense illumination. In the paper describing this fluorescence spectrum of iodine vapour it was pointed out that it was impossible to obtain the spectrum when the inserted tube containing the iodine vapour was made of combustion glass tubing. It was also pointed out that this glass tubing was found to be transparent to the light from the mercury are down to λ 2893∙7, and on account of this fact the conclusion was drawn that the light which stimulated the iodine vapour to the flurescence referred to must have had a shorter wave-length than λ 2893∙7.