C2. Commission on Symbols, Units, Nomenclature, Atomic Masses and Fundamental Constants (SUNAMCO)

Interim Activity Report

Brian W Petley , Chairman (IUPAP, C2)

1. Sponsorship of Conferences

The subject area of many of the particular physicists who are measuring fundamental constants also lies, of course, within the parts of physics covered by other IUPAP Commissions, and C2 takes care to avoid duplication of coverage. However, measuring quantities with the highest possible accuracy is as much a specialty as working in any other part of physics and so brings its own particular needs for the physicists concerned. These measurements as a group bring together scientists from a wide variety of physics and thereby provide important extra-disciplinary tests of particular aspects of theory at the highest accuracy. It is important for the subject that the physicists meet together as a group. An important part of the work is sponsoring conferences covering work in the above parts of physics and one such was the biannual Conference on Precision Measurement and Fundamental Constants (CPEM) held in Sydney, June 2000 which was sponsored by the Commission.

2. The SUN-AMCO Medal.

The Commission also sponsors the IUPAP SUN-AMCO Medal that is awarded to those physicists who have made outstanding contributions to the area of physics within the remit of the Commission. Its name commemorates the present Commission having derived from the merging of the IUPAP: SUN Commission and the AMCO Commissions.

The Commission is pleased to announce awards of Medals to Dr C A Hamilton and Professor T W Hänsch. Two further nominations have also been received and are presently under consideration by the Commission.

3. The ITU and Leap second

There has been some discussion of the problems associated with the introduction of leap seconds into disseminated Time Scales and their impact on the Global Satellite Navigation Systems. Thus Glonas uses Universal Cordinated Time (UTC) and the GPS uses the Atomic Time (AT). It is not clear at present whether these user problems are best solved by educating the user, by improving the associated software, or by making a fundamental change to the present system. The various timescales were introduced as a compromise because there was a variety of user needs that were judged impossible to meet by a single timescale.

4. The Fundamental Physical Constants

The CODATA Task Group on Fundamental Constants has produced a new set of Recommended Values for the Fundamental Physical Constants. These were published during 2000 (Rev. Mod. Phys. 72, 351 (2000)). These co-ordinate the measurements that were essentially available in published form to December 31st 1998. The new values replace the 1986 values. They represent a tenfold improvement in accuracy in many cases. The 1998 values have been universally accepted and are being rapidly introduced throughout the world. It is likely that there will be more frequent, interim, reviews than hitherto. These will have to be propagated with care if scientists are to be clear as to which particular review values colleagues are using.

5. Discovery and Naming of the Elements

Somewhere in most physics and chemistry text books there will be a list of the known elements and their agreed names and symbols. The synthesis and discovery of new heavy elements are made as much by the techniques of modern nuclear and atomic physicists as by those of chemistry, indeed since they tend to have short lifetimes they are not produced in great quantities. Their existence must usually be inferred by looking at the consequent chain of their decay products. However, there is considerable interest in synthesizing elements beyond element 110 because there has been the expectation that there will be an island of new elements of comparative stability.

Following a long established tradition, those who make the discoveries play a strong part in the decision concerning the name and symbol that is assigned to the new element. Consequently the names and symbols cannot be agreed ahead of discovery. IUPAC has issued an interim list of provisional names for as yet undiscovered elements.

This is a very difficult area of research and it is sometimes necessary for workers in this field to withdraw their claims to have discovered a new element. The discoveries of new elements have to be very carefully validated and established beyond doubt before their symbols and nomenclature can be agreed. The Commission has participated in the Joint IUPAC-IUPAP Transfermium Committee on the discovery of elements 110, 111, and 112. The findings in their report (IUPAC/ IUPAP Joint Working Group (JWG99), Discovery of the Elements 110-112) have been endorsed and accepted by IUPAC and IUPAP.

6. Units symbols and Nomenclature

Since 1931 the Commission has played a strong role in representing the interests of physicists concerning the symbols, units and nomenclature of science and technology to other organizations on behalf of IUPAP and IUPAP played a leading role in the setting up of the present International system of units (SI). The SI has enjoyed a period of comparative stability but is likely to be modified to a much greater extent in the future as other sciences and technologies become increasingly involved with such aspects of precise measurement. Generally speaking, if physicists had wanted changes to the existing SI they would have pressed for them. However, other sciences and technologies are also extensive users of the SI, and the SI is being increasingly modified to take account of their needs. Future Physicists are likely to use a sub-set of the SI rather than the SI as a whole. Thus, although many physicists may argue that the mole is not required (because they never need to use it), the mole is central to modern chemistry. The organizations to which C2 makes an input on behalf of IUPAP include: the International Standards Organization (ISO), the International Electrical Commission (IEC), the Consultative Committee on Units (CCU), the Joint Committee on Guides to Metrology (JCGM), the Interdivisional Committee on Symbols and Nomenclature (IDCNS) of the International Union of Pure and Applied Chemistry. All of these organizations have been busy producing new recommendations concerned with agreeing and integrating the symbols and terminology required to describe the measurements concerned with harmonizing new discoveries and technologies into a co-coordinated global system of universal usage. It is hoped to mount a strong effort during the next year to update the IUPAP publication IUP-25 in order to reflect these changes.

7. Vocabulary and uncertainties.

The JCGM has been actively considering the revised editions of the highly successful International Vocabulary on Metrology (VIM) and the Guide to the Expression of Uncertainty in Measurement (GUM). The revision of the former document is making slow progress, and the GUM is inevitably having additional supplements. It is hoped to produce a shortened version of the GUM. The latter has already had a major impact on measurement technology and largely reflects the methods long used by physicists.