Richard Day Deslattes, a senior fellow emeritus at NIST in Gaithersburg, Maryland, and a world leader in high-precision metrology, died on 16 May 2001 at his home in Rockville, Maryland, after a long battle with cancer.

Dick was born on 21 September 1931 in New Orleans, Louisiana, where he grew up. He received a BS degree in physics from Loyola University in New Orleans in 1952 and a PhD in physics in 1959 from the Johns Hopkins University, where he was strongly influenced by J. A. Bearden. The title of Dick’s thesis was “An Experimental Study of X-ray Attenuation Coefficients, 8–30 keV.”

Following a postdoctoral position at Cornell University, where he worked with Lyman Parratt, Dick joined the staff of the National Bureau of Standards (now NIST) in 1962, beginning an almost 39-year career that was extremely varied and productive. Throughout his career, Dick’s carefully chosen research plans revealed his broad interest in fundamental measurements of unprecedented precision; the selection of long-range aims, however, was determined by their relevance to crucial aspects of theoretical physics and chemistry. This purposefulness was grounded in Dick’s comprehensive grasp of the interface between lofty theory and reality as revealed by painstaking metrology.

Dick’s early years at NIST were devoted to spectroscopy of molecules and development of high-resolution x-ray spectrometers and powerful x-ray sources. In 1968, he became leader of a precision metrology and x-ray spectroscopy research group, a position he held for 33 years until his retirement at the end of April 2001. Throughout his entire career, Dick did not permit administrative duties to curtail his active involvement in laboratory experiments.

His early metrology efforts were directed toward the development of x-ray interferometry and the iodine-stabilized laser. In 1973, Dick produced the first combined x-ray and optical interferometer that was able to demonstrate the feasibility of accurate measurements of the lattice periods of silicon single crystals tied to the International System of Units (SI) definition of the meter. He led a multidisciplinary effort at NIST to combine the improved lattice-spacing measurements with new density and isotopic-abundance measurements to determine a value for the Avogadro constant with a defensible error budget near 10−6. The iodine-stabilized laser research led by Dick included characterization of this potential new length standard and comparisons with infrared radiation and the krypton length standard. This effort, along with contributions from other national measurement laboratories, led to the effective replacement of the krypton standard and the ultimate elimination of a separate length standard through a redefinition of the meter in 1983 based on the fixed speed of light.

In 1977, Dick became a senior NIST research fellow and led a major effort to use the accurately measured crystals to measure x-ray and gamma-ray wavelengths on a scale consistent with the SI definition of the meter. These measurements unified the optical to gamma-ray wavelength scales and eliminated the need for the x- and Å-units that were commonly used. The improved standards also had the effect of resolving discrepancies between theory and experiment for high-Z muonic atoms and establishing an improved value for the kaon mass.

Dick was a pioneer in the use of intense synchrotron radiation for atomic physics studies. He and his colleagues first (in 1978) used the Stanford Synchrotron Radiation Project. They then established an innovative beamline, X24A, at the Brookhaven National Synchrotron Light Source, where new discoveries such as x-ray selection of oriented molecules and polarization spectroscopy occurred.

During the period 1980 to 1981, Dick took a leave of absence to serve as director of NSF’s physics division. Dick and his colleagues initiated a long-term study of the systematics of neutral-atom x-ray spectra that included comparison with state-of-the-art theory. This effort recently produced a new, all-Z, x-ray wavelength database.

In 1983, Dick was honored by the Alexander von Humboldt Foundation in Bonn, Germany, with a Senior US Scientist Award. This award permitted him to participate in research collaborations from 1983 to 1984 in Germany at the University of Heidelberg and the GSI heavy-ion research center in Darmstadt, and at the Institut Laue-Langevin (ILL) in Grenoble, France. In the collaborations at Heidelberg and the GSI, Dick applied high-resolution, crystal-diffraction spectroscopy to studies of the spectra of highly stripped ions produced by large accelerators. These measurements provided stringent tests of the theory of quantum electrodynamics. The collaboration at the ILL developed into a world-class gamma-ray spectroscopy facility, which is still active today and emphasizes nuclear and solid-state physics as well as precision measurements. These measurements have recently included an accurate determination of the deuteron binding energy that has led to an improved value for the neutron mass and extension of the SI-based gamma-ray wavelength measurements into the 6-MeV region.

In 1990, Dick received the SUN-AMCO Medal, awarded by the International Union of Pure and Applied Physics, for his program to measure the Avogadro constant, his measurement of x- and gamma-ray wavelengths, and his development of ultrahigh-resolution gamma-ray spectroscopy.

Dick gave generously of his time to the scientific community, organizing international symposia and serving on committees, panels, and governing bodies. From 1985 to 1986, he was chair of what is now the APS division of atomic, molecular, and optical physics. He served on the editorial board of Physical Review A from 1999 to his death.

Dick was ready to listen to colleagues’ problems and willing to go beyond the call of duty by helping to apply his precision optical and x-ray measurement techniques. He was highly esteemed by a large circle of collaborators. These interactions flourished as a result of Dick’s willingness to share responsibility and his appreciation for the strengths of the contributing scientists, at NIST and worldwide. On the occasion of his retirement in April 2001, Dick noted that it had been his pleasure actually to have participated in an experiment or written a paper with almost everyone in the large gathering assembled to honor him. Those of us who had the privilege of collaborating with Dick know that the pleasure was ours.

Richard Day Deslattes