Review Articles Devoted to the Metrology of Electrical Units and Related Physical Constants

Abstract

The fundamental physical constants and the base units of measurement occupy positions of great importance in physics, not only through their foundation role in the edifice of science but through their interplay with the most advanced research in measurement science and in basic science, both theoretical and experimental. Not infrequently has one found the precision of experiments limited by that of the standard used in the realization of the pertinent unit(s) and new research is thereby stimulated to improve (or even replace) the existing standard(s). The periodic adjustment of the physical constants sometimes reveals inconsistencies that call for new measurement, new theory, or both. Discoveries in basic research are from time to time developed into new means for realizing the base units, as well as contributing to the consistency evaluation work.Physicists in general, and readers of Metrologia in particular, can therefore find it immensely rewarding to remain abreast of all such developments; to this end, Metrologia makes an important contribution by publishing both research papers and seminal review articles. It was with the latter particularly in mind that L Bliek and V Kose of the Physikalisch-Technische Bundesanstalt (PTB) proposed making a special effort to publish selected review papers from a session on Quantum Metrology and Electronic Methods in Fundamental Constants at the XXIInd General Assembly of the International Union of Radio Science (URSI), held in Tel Aviv, Israel, from August 24th to September 2nd 1987.This suggestion and a concomitant offer to recruit authors and furnish major editorial assistance were accepted with enthusiasm and alacrity. As the outcome, we foresee publishing some seven or eight review articles devoted to the metrology of electrical units and related physical constants. These will appear in successive issues of Metrologia, commencing with the present one, two or three at a time. The first three comprise: Precision Measurements of the Rydberg Constant by D H McIntyre and T W Hänsch, Present state of Quantized-Hall-Resistance Metrology by F Delahaye, and Present Understanding of the Quantum Hall Effect by L Bliek.The original intention had been to publish the reviews as they were presented in Tel Aviv. However, as attendees at the URSI meeting will doubtless perceive, some authors will be taking very recent new results into account. Nevertheless, the associate editors continue to hope for a minimum of delay in publishing these articles in view of the following near-future developments. The Comité Consultatif d'Electricité (CCE), at its meeting in September 1988, intends to adopt values for the frequency-to-voltage ratio based on the ac Josephson effect and for the quantized Hall resistance. As a result, from January 1st 1990, for the representation of the electrical units volt and ohm one expects to have world-wide uniformity as well as very close agreement with the SI units.