Incandescent Radiation from 3500 K Hot Clusters

Abstract

Hot refractory metal clusters have been produced by a novel experimental technique. A regenerative chemical cycle established in a high pressure microwave tungstenoxyhalide or rheniumoxide discharge leads to condensation of nanometer size tungsten or rhenium clusters with a mean temperature of about 3500 K or 4500 K, respectively. The clusters emit incandescent radiation with broad continuous spectra. The spectral shapes of the continua and the positions of their maxima (W 700 nm, Re 550 nm) are characteristic for the refractory metal. A first theoretical description of the clusters’ radiation can be based on the Mie theory. The existence of clusters with spherical shape and a mean size of about 2 nanometers has been proven by a laser scattering experiment. The properties of the cluster radiation especially the continuous spectrum and the high luminous efficiency are attractive for lighting applications.