The generation of light by chemical reactions in flash lamps

Abstract

In conventional combustion flash lamps the reaction between zirconium and oxygen is utilized to obtain a quantity of light. The spectral distribution is similar to that for blackbody radiation at about 4000°K. It is to be expected that larger quantities of light will be emitted if reactions leading to higher temperatures are used. Such reactions are distinguished from others by their favorable energy balance and the thermal stability of the reaction products. A first selection points to reaction of aluminum or zirconium with oxygen, fluorine or easily dissociated fluorine compounds—e.g., compounds with nitrogen or oxygen. Some of these reactions have been investigated in detail, with the following results:o(a)Reactions of zirconium with the above fluorine compounds lead to temperatures up to 4700°K; under special circumstances fluorine reactions emit larger quantifies of light than oxygen reactions.(b)If the available energy is emitted as the radiation of a black body of known temperatur, the maximum light output can be calculated. For several reactions these results agree with experiments.(c)During the reaction between zirconium and oxygen, the oxygen pressure decreases, which favors the formation of zirconium monoxide over that of zirconium dioxide. In this case, calculations predict a sharp decrease in heat generation. In order to keep the reaction going, more zirconium dioxide has to be formed, which is achieved by a moderate temperature decrease. This prediction is confirmed by experiments.(d)Light absorbing reaction products cause a significant difference between the amount of light generated and the quantity of light actually emitted. Analysis of the experimental results leads to the hypothesis that 450 lumenseconds/mg Zr are generated inside zirconiumoxygen lamps, and to an experimentally confirmed relation between the dimensions of the light bulb, the amount of combustibles and the quantity of light emitted. Reactions of zirconium with the above fluorine compounds lead to temperatures up to 4700°K; under special circumstances fluorine reactions emit larger quantifies of light than oxygen reactions. If the available energy is emitted as the radiation of a black body of known temperatur, the maximum light output can be calculated. For several reactions these results agree with experiments. During the reaction between zirconium and oxygen, the oxygen pressure decreases, which favors the formation of zirconium monoxide over that of zirconium dioxide. In this case, calculations predict a sharp decrease in heat generation. In order to keep the reaction going, more zirconium dioxide has to be formed, which is achieved by a moderate temperature decrease. This prediction is confirmed by experiments. Light absorbing reaction products cause a significant difference between the amount of light generated and the quantity of light actually emitted. Analysis of the experimental results leads to the hypothesis that 450 lumenseconds/mg Zr are generated inside zirconiumoxygen lamps, and to an experimentally confirmed relation between the dimensions of the light bulb, the amount of combustibles and the quantity of light emitted.