Fundamental Constants Data Center

Overview   |   Program Directions   |   Major Technical Highlights

Overview

• providing an international information center on the fundamental constants;
• periodically providing sets of recommended values of the constants for international use;
• administering the NIST Precision Measurement Grant (PMG) Program;
• providing the editorship of the Journal of Research of the National Institute of Standards and Technology; and
• interpreting the International System of Units (SI) for the United States.

Program Directions

• Information Center and Constants Adjustments. Maintain a fundamental constants library, a Web bibliographic database, respond to inquiries, and carry out the next Committee on Data for Science and Technology (CODATA) least-squares adjustment of the values of the constants.

• Precision Measurement Grants. Continue to fund proposals of the highest quality and that provide maximum benefit to NIST.

• Fundamental Constants Theory. Create an atomic theory bibliographic database and do calculations where needed for the theory used in evaluation of the fundamental constants.

• SI Units. Generate and disseminate publications related to the SI.

• Measurement Uncertainty. Under the auspices of the international Joint Committee for Guides on Metrology (JCGM), generate guides on expressing measurement uncertainty.

Major Technical Highlights

• Constants Wall Chart and Wallet Cards. Concurrent with the NIST centennial, thousands of copies of a wall chart and a wallet card giving subsets of the 1998 CODATA recommended values of the fundamental constants of physics and chemistry (the most current) were distributed to physicists, chemists, other scientists, engineers, and students throughout the world.

• Centennial Issue of NIST Journal of Research. To commemorate the NBS/NIST centennial on March 3, 2001, the January-February 2001 issue (Vol. 106, No. 1) of the Journal of Research of the National Institute of Standards and Technology was published as the Centennial Issue under the title "NBS/NIST --— 100 Years of Measurement." The 370 page issue contains 12 articles, all centered on measurement recognizing that since its founding in 1901, NBS/NIST has served as the Nation’s National Metrology Institute (NMI). Indeed, metrology has been the foundation upon which the institution has rested for the first 100 years of its existence. The Centennial Issue is available on the Web at http://www.nist.gov/jres.

• Theory of the Hydrogen Atom. Precise theoretical predictions of the properties of hydrogen are important, not only to test our understanding of this basic atom, but also to provide information on the fundamental physical constants, such as the Rydberg constant. Over the past several years, a NIST-led project has carried out a precise computation of the most basic quantum electrodynamic (QED) effect in the spectrum of hydrogen, namely the radiative process in which the atom emits and then reabsorbs a photon (the quantum of electromagnetic radiation). This process results in shifts of the atomic energy levels, which, in turn, determines the frequencies of light that are emitted and absorbed in experiments. The calculation was carried out for the 1S, 2S, and 2P states of hydrogen. By employing intensive, high-performance parallel computation, with CPU times of the order of months, the project has led to a reduction of the uncertainty in the one-photon QED effect by over three orders of magnitude. This work was the result of a collaboration between NIST and the Technical University of Dresden, Germany, and is described as a "spectacular success" in Physics Reports 342, 63 (2001).

• New Publication on the SI. The 2001 Edition of NIST Special Publication (SP) 330, The International System of Units (SI) is now available. It is the U.S. version of the English text of the seventh edition (the most recent) of the definitive international reference on the SI, the modern metric system, published in 1998 by the International Bureau of Weights and Measures (BIPM) under the title Le Système International d’Unités (SI). However, the 2001 Edition of SP 330 also incorporates the contents of Supplément 2000: additions et corrections à la 7^e édition (1998) published by the BIPM in June 2000. The 2001 edition of SP 330 replaces its immediate predecessor, the 1991 edition, which was based on the sixth edition of the BIPM SI publication.

• New Precision Measurement Grants. Two new NIST Precision Measurement Grants have been awarded. One was made to Prof. Mohideen of the University of California at Riverside for the project entitled "Precision Measurements of the Casimir Force Using an Atomic Force Microscope." The aim of the research supported by this grant is to make high precision measurements of the Casimir force between small metallic objects. The Casimir force is the result of the effect that the objects have on the electromagnetic fluctuations in the vacuum in the space between them. This force can be significant at distances less than 100 nm, and so it plays an important role in the mechanical properties of artificial microstructures. The proposed research will increase the precision of measurements of the Casimir force by over a factor of 10,000 and will measure the temperature dependence of the force.
  The other grant was made to Prof. Schoelkopf of Yale University for the project entitled "Development of an Electron-Counting Ammeter." The aim of the research supported by this grant is to make a device to measure electric current (an ammeter) based on measurement of the frequency of voltage oscillations across a tunnel junction that allows only one electron at a time to pass through. Such a device could only measure small currents, however a sufficient number in parallel could measure a current that would be large enough to allow fundamental tests of present day resistance and voltage standards based on quantum devices. An electron-counting ammeter is more likely to be scalable to such a use than the analogous single electron pumps which already exist.