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History of Atomic Spectroscopy at NIST

The Atomic Spectroscopy Group at the National Institute of Standards and Technology (NIST) has a long history of contributions to optical science and metrology. The Group was headed for many years by William F. Meggers, who early in his career used interferometric methods to measure the index of refraction of air over a wide wavelength region. Later he spearheaded the development of infrared sensitive emulsions, which he used for aerial photography and to photograph the sun in the infrared. His great interest in spectroscopy led him to investigate the spectra of nearly every element, and in the process lay the foundation for modern analytical spectroscopy. In order to organize and disseminate the vast amount of information on atomic spectra and energy levels that had accumulated through the years, Meggers brought Charlotte Moore Sitterly to NIST. Charlotte Sitterly published the classic volumes on Atomic Energy Levels and established what today has become the NIST Data Centers on Atomic Spectroscopy. These Data Centers, one on Atomic Energy Levels and one on Atomic Transition Probabilities and Line Shapes, carry out critical compilations and maintain large databases of atomic spectroscopic data, most of which are available on the World Wide Web.

When Meggers retired from NIST in 1958, he was succeeded as leader of the group by Karl G. Kessler. After a few years Kessler went on to higher management at NIST. In 1961 William C. Martin began a leadership of the Group that lasted nearly forty years. In the early years of his leadership the Group greatly expanded in number of staff members, and its interests were broadened to include precision measurements by laser spectroscopy and applications to astrophysics and diagnostics of plasmas found in fusion research devices and commercial lighting devices. Although astronomers had always been prime users of spectroscopic data, the advent of space-based observatories intensified this application, especially though the pressing need for extensive spectroscopic data in the vacuum ultraviolet. Martin retired in 1998 and was succeeded as Group Leader by Joseph Reader. Although officially retired, Martin continues actively as Scientist Emeritus.

Current laboratory projects of the Group include data for space astrophysics, high precision measurements by Fourier transform and laser spectroscopy, high accuracy measurements of light sources used for wavelength calibration of microlithography lasers, data on highly-ionized atoms for diagnostics of fusion energy devices, development of methods for diagnostics of high-intensity lighting sources by x-ray absorption and fluorescence, and tests of the use of image plates for vacuum ultraviolet spectroscopy. Data Center projects include compilations of wavelengths and energy levels for the rare gases, tungsten, rubidium, cesium, barium, beryllium, and gallium in all stages of ionization. Transition probabilities are being compiled for Fe I and Fe II, Na in all stages of ionization, and other light elements of astrophysical importance, such as S, Si, Mg, and Ne. Our web-based databases such as the Atomic Spectra Database and the Bibliographic Database on Atomic Transition Probabilities continue to be expanded and improved. Theoretical work is carried out on electron impact cross sections for excitation and ionization of atoms and molecules for fusion science applications. These results are also available on the World Wide Web.