Abstract :
Recent spectroscopic investigations by the National ireau of Standards (NBS) give positive identification of two :v artificial elements. Not found in nature, the elements :hnetium (Tc) and promethium (Pm) are by-products of anium fission; they were supplied by the Atomic Energy Dmmission. Studies at the NBS of the first optical spectra these elements have revealed many properties of the atoms id their nuclei. They also have provided reliable wavengths and intensity data for about 5,000 new spectral lines. In 1949 the NBS received from the Oak Ridge National iboratory several milligrams of each of these fission prodts for the purpose of making reliable descriptions and analyse of the spectra characteristic of these artifical eleents. Four milligrams of highly pure Tc were used to mtograph arc and spark emission spectra with a large difiction grating. The spectra were recorded several times m 2,200 to 9,000 angstroms, and between these limits the avelengths and relative intensities of about 2,300 radia- )ns characteristic of Tc atoms and ions were determined. While comparing intensities in arc and spark excitation, the les could be assigned definitely either to neutral Tc atoms to singly ionized atoms.
