The Fundamental Physical Constants

established in 1966 as an interdisciplinary committee of the International Council of Scientific Unions (now the International Council of Science). Three years later, CODATA created the task group on fundamental constants to periodically provide the scientific and technological communities with a self-consistent set of internationally recommended values for the basic constants and conversion factors of physics and chemistry. Under the auspices of the task group, we have completed a new least-squares adjustment of those values—termed the 2002 adjustment— that takes into account all relevant data available through 31 December 2002.1 The accompanying tables give the 2002 CODATA recommended values resulting from that adjustment, except for some specialized x-ray-related quantities and various natural and atomic units. The complete 2002 CODATA set of more than 300 recommended values, together with a detailed description of the data and their analysis, is given in reference 1. All of the values, as well as the correlation coefficients between any two constants, are available online in a searchable database provided by NIST’s fundamental constants data center. The internet address is http://physics.nist.gov/constants. The 2002 CODATA set replaces its immediate predecessor, which resulted from the 1998 adjustment,2 also carried out under the auspices of the task group. Only four years have elapsed between the 31 December 1998 and 31 December 2002 closing dates of the two adjustments (12 years separated the 1998 adjustment and its predecessor), but a number of advances in experiment and theory have led to improvements in our knowledge of the values of the constants. The new information includes measurements of the Newtonian constant of gravitation G; improved experimental values of the relative atomic masses of helium-4, oxygen-16, and cesium-133 (carbon-12 has a relative atomic mass of exactly 12, by definition); a more accurate value of the 1S1/2–2S1/2 transition frequency in hydrogen; a new result for the bound-state root-mean-square (rms) charge radius of the proton Rp; and highly accurate measurements related to the bound-state g-factor of the electron in the hydrogenic ions 12C5⊕ and 16O7⊕. Additional experimental refinements include a new, quite accurate measurement of the muon magnetic moment anomaly am; an accurate value, obtained from the atomic recoil frequency shift of photons absorbed and emitted by Cs atoms, for the quotient h/m(133Cs), where h is the Planck constant and m(133Cs) is the mass of the 133Cs atom; a result for the molar volume of silicon Vm(Si); and new experimental findings concerning previous measurements of the {220} lattice spacing of particular Si crystals. Theorists have developed improved expressions for the hydrogen and deuterium energy levels, the electron and muon magnetic moment anomalies ae and am, the ground-state hyperfine splitting of muonium (that is, the me “atom”), and the electron bound-state g-factor in hydrogenic ions.