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

Commission on Symbols, Unit, Nomenclature, Fundamental Constants and Atomic Masses
September 2005

Chair: Kumar S. Sharma (Canada)
Co-chair: Georges Audi (France)
Secretary: Leslie Pendrill (Sweden)

Members:

Paul De Bievre (Belgium)
Myung Sai Chung (Korea)
Jeffrey Flowers (UK/NPL)
Matti Leino (Finland)
Alinka Lepine-Szily (Brazil)
Savely Karshenboim (Russia)
Peter Mohr (USA/NIST)
Atsuo Morinaga (Japan)
Yu-Xin Nie (China)
Wolfgang Woeger (Germany)

Conferences:

C2 has sponsored two major conferences in the past. They were both held in 2004. We do not expect to have any conferences to put forward for sponsorship in 2005. They were:

1. 4th International Conference on Exotic Nuclei and Atomic Masses (ENAM)

• September 12-16, 2004, Pine Mountain, Georgia, USA http://www.phy.ornl.gov/enam04/.
• This conference is widely attended by those members of C2 with interests in Atomic Masses and serves as a point of contact for C2 members. It has been traditionally supported by C2
• This conference was sponsored by IUPAP
• Next session in 2008 in Poland

2. CPEM (UK)

• Held 27 th of June – 2 nd of July, 2004, London, UK.
• Widely attended by those members of C2 involved in Precision Measurements.
• Serves as a point of contact for those C2 members.
• This meeting has been traditionally supported by C2. Unfortunately, IUPAP did not sponsor or support this conference in 2004 because it did not meet the requirements for conference fees.

Publications:

1. IUPAP-25 Booklet on Symbols, Units, Nomenclature and Fundamental Constants

• Many requests are still received for the existing version of this “little red book”.

Liaisons with other organizations:

Contacts between IUPAC and IUPAP SUNAMCO have occurred during the period of this report. Amongst others, SUNAMCO was kindly invited by IUPAC Analytical Chemistry Division to its meeting (040217, IAEA, Vienna) to discuss increased collaboration as well as to the IUPAC General Assemblies, through the ICTNS . Items discussed included:

• cooperation about terminology (initial contacts have been made with David Moore (Los Alamos) who is active in producing the latest Orange book)

• a possible joint project about Metrological Traceability. A proposal to ICSU entitled “Measurement Traceability – A Fair Basis For Trade” lead by IUPAC, together with IUPAP and UNIDO, unfortunately did not get a positive response.

• presentation of a talk at a Minisymposium “Emerging issues in Metrology in Chemistry”.

Works by members:

Atomic Mass Evaluations: Audi et al published a New Atomic Mass Evaluation in 2003.

A group of commission members and scientists involved in the measurement of atomic masses met at the recent ENAM’04 meeting to discuss the future of the Atomic Mass Evaluations. These evaluations of experimental data (and sometimes estimates from extrapolation of the surface of masses for values that are not available from experiment) on atomic masses have been carried out since the early 1950’s at intervals of approximately 4 years. The goal of the evaluation is to produce a self-consistent, recommended set a atomic masses for use by the scientific community and others. When combined with the natural abundances of the isotopes these mass values also yield the atomic weights that are commonly used in chemistry. Audi (vice-chair, C2) and Wapstra have carried out the most recent evaluations. Concerns were expressed about the continuation of this important work in the future after the current authors retire. Audi offered to train someone to take over the task should a candidate be found. The possibility of funding the work in a permanent manner was discussed. It was felt that some endorsement and support from IUPAP for this work could be instrumental in obtaining the resources needed.

New Values for Fundamental Constants: Accurate values of fundamental physical constants, such as the elementary charge e, Planck constant h, fine-structure constant a , and Avogadro constant N A, are of great importance to the scientific and technological communities because they are required in many practical calculations. In December, 2003, the new self-consistent set of values of over 300 basic constants and conversion factors of physics and chemistry recommended by the Committee on Data for Science and Technology (CODATA) for international use first became available for scientists worldwide on the U.S. National Institute of Standards and Technology (NIST) Physics Laboratory Web site at http://physics.nist.gov/constants.

The new set of constants is the result of the 2002 least-squares adjustment of their values carried out by Peter Mohr and Barry Taylor at NIST under the auspices of the CODATA Task Group on Fundamental Constants. The CODATA Task Group, chaired by Mohr since 1999 and by Taylor before that, with members from ten countries and one member from the International Bureau of Weights and Measures (BIPM), meets annually and reviews the data selection and methodology of the adjustment in order to provide an international consensus on the final values. The new set of values, based on all the data available through December 31, 2002, replaces its immediate predecessor recommended four years earlier by CODATA, which resulted from the 1998 least-squares adjustment also carried out by Mohr and Taylor under Task Group auspices.

Discussions and recommendations:

The Dalton: In response to the increase in the use of the name “dalton” for the unified atomic mass unit among chemists, it was suggested by IUPAC that the unified atomic mass unit (u) be renamed the “dalton” (D). The definition of the unit would remain unchanged as one-twelfth the mass of a neutral 12C atom in its ground state. After considerable discussion it was agreed that both units, u and D, should be allowed official use and that the situation be reexamined in the future to evaluate whether the use of these units in the scientific community would suggest the selection of one of these names over the other. Some members have argued that there is no strong reason to change the name of this unit.

The Uno: The introduction of a name, “uno”, for the unit one in SI was proposed by the CCU of the BIPM (see René Dybkaer, Metrologi a, 41 (2004) p.69-73) . It was decided that because of the potential inconsistencies that might result from the introduction of such a unit, the commission could not support the introduction of this new unit. The matter has been dropped for the time being by the CCU

The definition of the kilogram:

An active and extensive discussion of the recent proposal to redefine the kilogram (see “Redefinition of the kilogram: a decision whose time has come" by Ian M. Mills et al. in Metrologia 42 (2005) 71-80) among commission members resulted in the following recommendation to IUPAP:

• efforts be continued to refine experiments that link the unit of mass to fundamental constants with a view to improving the connection between macroscopic and microscopic masses and the realization of macroscopic mass measurements in terms of a fundamental definition of the kilogram
• the proper time for the redefinition of the kilogram and ampere would be when it can be determined that the advantages in having precision electrical measurements expressed in terms of the SI volt and ohm and in having improved precision of the values of the fundamental constants outweigh the disadvantage of using the prototype as the practical mass unit for macroscopic mass measurements

The full text of the recommendation may be obtained from the Chair of the commission C2: SUNAMCO.

SUNAMCO Medals: One medal was awarded for achievement and service in the field of atomic mass measurements to:

• A.H. Wapstra (NIKHEF) for his role in the Atomic Mass Evaluations from their inception to the present.

http://www.iupac.org/divisions/V/index.html

IUPAC Interdivisional Committee on Terminology, Nomenclature and Symbols (ICTNS)

http://www.iupac.org/divisions/V/news/040217/index.html; Pendrill L R 2005 "Meeting future needs for Metrological Traceability – A physicist’s view", Accred. Qual. Assur., 10, no 3, 133 - 9

New Values for Fundamental Constants: Accurate values of fundamental physical constants, such as the elementary charge e, Planck constant h, fine-structure constant a , and Avogadro constant N A, are of great importance to the scientific and technological communities because they are required in many practical calculations. In December, 2003, the new self-consistent set of values of over 300 basic constants and conversion factors of physics and chemistry recommended by the Committee on Data for Science and Technology (CODATA) for international use first became available for scientists worldwide on the U.S. National Institute of Standards and Technology (NIST) Physics Laboratory Web site at http://physics.nist.gov/constants.

The new set of constants is the result of the 2002 least-squares adjustment of their values carried out by Peter Mohr and Barry Taylor at NIST under the auspices of the CODATA Task Group on Fundamental Constants. The CODATA Task Group, chaired by Mohr since 1999 and by Taylor before that, with members from ten countries and one member from the International Bureau of Weights and Measures (BIPM), meets annually and reviews the data selection and methodology of the adjustment in order to provide an international consensus on the final values. The new set of values, based on all the data available through December 31, 2002, replaces its immediate predecessor recommended four years earlier by CODATA, which resulted from the 1998 least-squares adjustment also carried out by Mohr and Taylor under Task Group auspices.

Discussions and recommendations:

The Dalton: In response to the increase in the use of the name “dalton” for the unified atomic mass unit among chemists, it was suggested by IUPAC that the unified atomic mass unit (u) be renamed the “dalton” (D). The definition of the unit would remain unchanged as one-twelfth the mass of a neutral 12C atom in its ground state. After considerable discussion it was agreed that both units, u and D, should be allowed official use and that the situation be reexamined in the future to evaluate whether the use of these units in the scientific community would suggest the selection of one of these names over the other. Some members have argued that there is no strong reason to change the name of this unit.

The Uno: The introduction of a name, “uno”, for the unit one in SI was proposed by the CCU of the BIPM (see René Dybkaer, Metrologi a, 41 (2004) p.69-73) . It was decided that because of the potential inconsistencies that might result from the introduction of such a unit, the commission could not support the introduction of this new unit. The matter has been dropped for the time being by the CCU

The definition of the kilogram:

An active and extensive discussion of the recent proposal to redefine the kilogram (see “Redefinition of the kilogram: a decision whose time has come" by Ian M. Mills et al. in Metrologia 42 (2005) 71-80) among commission members resulted in the following recommendation to IUPAP:

• efforts be continued to refine experiments that link the unit of mass to fundamental constants with a view to improving the connection between macroscopic and microscopic masses and the realization of macroscopic mass measurements in terms of a fundamental definition of the kilogram
• the proper time for the redefinition of the kilogram and ampere would be when it can be determined that the advantages in having precision electrical measurements expressed in terms of the SI volt and ohm and in having improved precision of the values of the fundamental constants outweigh the disadvantage of using the prototype as the practical mass unit for macroscopic mass measurements

The full text of the recommendation may be obtained from the Chair of the commission C2: SUNAMCO.

SUNAMCO Medals: One medal was awarded for achievement and service in the field of atomic mass measurements to:

• A.H. Wapstra (NIKHEF) for his role in the Atomic Mass Evaluations from their inception to the present.