Peter J. Mohr

CODATA recommended values of the fundamental physical constants: 2006 *

This paper gives the 2006 self-consistent set of values of the basic constants and conversion factors of physics and chemistry recommended by the Committee on Data for Science and Technology (CODATA) for international use. Further, it describes in detail the adjustment of the values of the constants, including the selection of the final set of input data based on the results of least-squares analyses. The 2006 adjustment takes into account the data considered in the 2002 adjustment as well as the data that became available between 31 December 2002, the closing date of that adjustment, and 31 December 2006, the closing date of the new adjustment. The new data have led to a significant reduction in the uncertainties of many recommended values. The 2006 set replaces the previously recommended 2002 CODATA set and may also be found on the World Wide Web at physics.nist.gov/constants.

Redefinition of the kilogram, ampere, kelvin and mole: a proposed approach to implementing CIPM recommendation 1 (CI-2005)

The International System of Units (SI) is founded on seven base units, the metre, kilogram, second, ampere, kelvin, mole and candela corresponding to the seven base quantities of length, mass, time, electric current, thermodynamic temperature, amount of substance and luminous intensity. At its 94th meeting in October 2005, the International Committee for Weights and Measures (CIPM) adopted a recommendation on preparative steps towards redefining the kilogram, ampere, kelvin and mole so that these units are linked to exactly known values of fundamental constants. We propose here that these four base units should be given new definitions linking them to exactly defined values of the Planck constant h, elementary charge e, Boltzmann constant k and Avogadro constant NA, respectively. This would mean that six of the seven base units of the SI would be defined in terms of true invariants of nature. In addition, not only would these four fundamental constants have exactly defined values but also the uncertainties of many of the other fundamental constants of physics would be either eliminated or appreciably reduced. In this paper we present the background and discuss the merits of these proposed changes, and we also present possible wordings for the four new definitions. We also suggest a novel way to define the entire SI explicitly using such definitions without making any distinction between base units and derived units. We list a number of key points that should be addressed when the new definitions are adopted by the General Conference on Weights and Measures (CGPM), possibly by the 24th CGPM in 2011, and we discuss the implications of these changes for other aspects of metrology.

QED corrections in heavy atoms

Abstract The comparison of theory and experiment for energy levels of strongly bound electrons provides a critical test of quantum electrodynamics in strong fields. A theoretical evaluation of the vacuum polarization and self energy radiative corrections to electron binding energies in heavy atoms is given. The calculations are done to all orders in the strength of the external field of the nucleus Zα . The influence of nuclear size and structure effects is investigated. The results for the Lamb shift are compared to the experimental data.

Redefinition of the kilogram: a decision whose time has come

The kilogram, the base unit of mass in the International System of Units (SI), is defined as the mass of the international prototype of the kilogram. Clearly, this definition has the effect of fixing the value of to be one kilogram exactly. In this paper, we review the benefits that would accrue if the kilogram were redefined so as to fix the value of either the Planck constant h or the Avogadro constant NA instead of , without waiting for the experiments to determine h or NA currently underway to reach their desired relative standard uncertainty of about 10−8. A significant reduction in the uncertainties of the SI values of many other fundamental constants would result from either of these new definitions, at the expense of making the mass of the international prototype a quantity whose value would have to be determined by experiment. However, by assigning a conventional value to , the present highly precise worldwide uniformity of mass standards could still be retained. The advantages of redefining the kilogram immediately outweigh any apparent disadvantages, and we review the alternative forms that a new definition might take.

The Fundamental Physical Constants

Incorporating recent data, a new set of recommended values of the basic constants and conversion factors of physics and chemistry has just been issued.

CODATA recommended values of the fundamental constants

A review is given of the latest Committee on Data for Science and Technology (CODATA) adjustment of the values of the fundamental constants. The new set of constants, referred to as the 1998 values, replaces the values recommended for international use by CODATA in 1986. The values of the constants, and particularly the Rydberg constant, are of relevance to the calculation of precise atomic spectra. The standard uncertainty (estimated standard deviation) of the new recommended value of the Rydberg constant, which is based on precision frequency metrology and a detailed analysis of the theory, is approximately 1/160 times the uncertainty of the 1986 value. The new set of recommended values as well as a searchable bibliographic database that gives citations to the relevant literature is available on the World Wide Web at physics.nist.gov/constants and physics.nist.gov/constantsbib, respectively.

Calculation of the Electron Self Energy for Low Nuclear Charge

We present a nonperturbative numerical evaluation of the one-photon electron self-energy for hydrogenlike ions with low nuclear charge numbers

Convergence acceleration via combined nonlinear-condensation transformations

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On the Redefinition of the Kilogram

to 5. Our calculation for the

Electron Self-Energy for the K and L Shells at Low Nuclear Charge

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