Date: Thu, 16 Jan 2014 11:03:12 +0100 From: Atomic Mass Data Center To: Recipients of AMDC bulletin Subject: News from the Atomic Mass Data Center (AMDC) - January 2014 EVALUATIONS and COMPILATIONS G.Audi, F.G.Kondev, M.Wang Dear Colleagues, We would like to make you aware of a publication entitled "Atomic Mass Compilation 2012", which is due to appear in the March 2014 issue of the journal Atomic Data and Nuclear Data Tables (available online on September 6, 2013). We would like to make it clear that this paper is not endorsed by the Atomic Mass Evaluation (AME) international collaboration. The AME provides carefully recommended evaluated data, published periodically. The "Atomic Mass Compilation 2012" is not to be associated with the latest publication, AME2012, nor with any of the previously published mass evaluations that were developed under the leadership of Prof. A.H. Wapstra. We found the data presented in "Atomic Mass Compilation 2012" to be misleading and the approach implemented to be lacking in rigour since it does not allow to unambiguously trace the original published mass values. Furthermore, the method used in "Atomic Mass Compilation 2012" is not valid and leads to erroneous and contradictory outputs, resulting in confusion and consequently misleads the adjustments made by theoreticians when fitting their parameters to a table of experimental masses, or when performing calculations of astrophysical processes, or of new nuclear reactors characteristics, or of management of nuclear wastes. We tried in a good faith to resolve those issues with the authors of the AMC12 article, but unfortunately we were not successful. On December 13, 2013 together with some of the most eminent physicist involved in the domain of the masses of nuclei, a "Comment" was submitted to the Atomic Data and Nuclear Data Tables journal regarding the above article. It is reproduced below. A printed version is available from arXiv. http://arxiv.org/abs/1401.2021 We deeply regret the present situation. Best regards, G. Audi, F.G. Kondev, and M. Wang PREVIOUS BULLETINS OF THE AMDC Previous bulletins of the AMDC can be accessed, as usual, via: http://amdc.in2p3.fr/bulletins/filel.html ---------------- Comment submitted to "Atomic Data and Nuclear Data Tables" 13.12.2013 by G.Audi, K.Blaum, M.Block, G.Bollen, F.Herfurth, S.Goriely, J.C.Hardy, F.G.Kondev, H.-J.Kluge, D.Lunney, J.M.Pearson, G.Savard, K.Sharma, M.Wang, Y.H.Zhang For more than half a century the Atomic Mass Evaluation (AME) has striven to provide a consistent and comprehensive set of atomic masses (see Ref. [1=964] and references therein). Masses are measured directly by mass spectrometry techniques or deduced from energy measurements in nuclear decays and reactions. In all cases, mass relations are established between two or more nuclides, thus resulting in a large number of links that are meticulously evaluated to ultimately obtain the masses for all known nuclei using a least-squares-fit approach to all available experimental data. Those carefully recommended values play a seminal role in fundamental research in many areas of natural sciences (chemistry, physics, astrophysics, material physics, etc) and in an increasingly large number of applications. For example, the 2003 edition AME2003 [1,2] has been cited more than 2150 times according to Web of Science. The most recent evaluation, AME2012 [3,4], and the associated evaluation of nuclear properties, NUBASE2012 [5], were published in the December 2012 issue of the journal Chinese Physics C by a collaboration of scientists from Europe, China and the USA. The AME approach and its long history are in contrast with the recent publication of the so-called Atomic Mass Compilation (AMC12) [6]. We, as regular users or contributors of the AME mass tables, wish to highlight several major differences between AMC12 and the traditional AME series. It is not the purpose of this "Comment" to give an extensive list of all discrepancies and reasons why the AMC12 deviates from the recommended values in AME2012. As a general rule, any credible evaluation must contain an extensive compilation of all available experimental data. Indeed such a compilation is a prerequisite of the AME process and it has already been published in the latest AME2012 [3,4]. In this respect AMC12 does not add anything new to what has already been published, but instead it extensively uses material from AME2012, without referring to the original AME collaboration in that context. Furthermore, although it is certainly necessary, a compilation is not sufficient to provide a consistent set of values and this is exactly where the AMC12 falls well short of AME2012. In the AME process, each piece of data is expressed as a linear relation where the masses are treated as unknown parameters. The ensemble of relations is solved by the least- squares method, which requires inversion of the associated normal matrix. One obvious advantage of the AME matrix approach over the simple averages used in AMC12 is that it employs an overdetermined data set, which allows for the evaluation of consistencies (or conflicts). By contrast, the method used in AMC12 is to combine any new result with the mass values from the previous AME2003, independent of any other new result, even if it is reported in the same paper. Given that many data have changed -and improved -since 2003, this procedure can only yield results that are less precise and, even worse, less accurate. Correlations are ignored in AMC12, even though the AME has proven that they are essential, given the strong entanglement of much of the input data. Furthermore, in AMC12 the individual pieces of experimental data (decay and/or reaction energies, etc.) are not given, but instead they have been converted into mass-excesses, preventing easy access to the originally published values. As a final remark, we urge the readers and users of mass tables not to be misled by the similarity of the titles of "The AME2012 atomic mass evaluation" [3,4] with the AMC12 presented as "Atomic mass compilation 2012" [6]. We would like to stress that the AMC12 is by no means the continuation or an update of the work initiated by A.H. Wapstra in the 1950=92s. The methods used in the AME series have consistently proved themselves and have led to useful and reliable tables of atomic masses from the ensemble of experimental data obtained since 1934, and from all laboratories around the world. The AME2012 and the past AME evaluations were all endorsed by the C2 Commission on Symbols, Units, Nomenclature, Atomic Masses and Fundamental Constants of the International Union of Pure and Applied Physics (IUPAP) whose aim is to promote international agreements on the use of symbols, units, nomenclature and standards. The AME is a coordinated effort that involves collaboration between several scientists from around the world. They make no claim to a monopoly on the world=92s mass data. However, because of the comprehensive approach used by the AME collaboration, we consider the AME of superior accuracy to the more simplistic AMC12 compilation. We hope that any confusion between the AME and the so-called AMC12 will not interfere with the increasing use of mass data for fitting mass models and for the critical applications of masses in nuclear energy, and elsewhere.