A search for an improved ultraviolet radiation source

Abstract

This work examines the spectral modifications produced in high-pressure mercury discharge lamps by the iodides of iron, cobalt, manganese and antimony, both individually and in select combinations, at a lamp operating power of 1000 W. Individually, iron, cobalt and manganese iodide additives significantly improve the UVA spectral output at wavelengths beneficial to either the diazo photoprint or suntan application. Increasing the iodide quantity strongly depresses the radiation emitted in the UVB and UVC spectral regions. A select combination of iron and cobalt iodides, with mercury, enhances the UVA spectral response to a level beyond that achieved by the individual iodides alone. This combination has been used to develop a lamp with a spectrum covering adequately both the suntan and photoprint applications. None of the iodides in this trial improved on the performance of mercury in the UVC spectral region, supporting the view that water sterilisation may best be served by lamps dosed only with mercury.