The AME 2020 atomic mass evaluation (I). Evaluation of input data,and adjustment procedures

This is the first of two articles(Part I and Part II)that presents the results of the new atomic mass evaluation,Ame2020.It includes complete information on the experimental input data that were used to derive the tables of recommended values which are given in Part II.This article describes the evaluation philosophy and procedures that were implemented in the selection of specific nuclear reaction,decay and mass-spectrometric data which were used in a least-squares fit adjustment in order to determine the recommended mass values and their uncertainties.All input data,including both the accepted and rejected ones,are tabulated and compared with the adjusted values obtained from the least-squares fit analysis.Differences with the previous Ame2016 evaluation are discussed and specific examples are presented for several nuclides that may be of interest to Ame users.     

The Ame2020 atomic mass evaluation (Ⅰ). Evaluation of input data,and adjustment procedures

This is the first of two articles(Part I and Part II) that presents the results of the new atomic mass evaluation, Ame2020. It includes complete information on the experimental input data that were used to derive the tables of recommended values which are given in Part II. This article describes the evaluation philosophy and procedures that were implemented in the selection of specific nuclear reaction, decay and mass-spectrometric data which were used in a least-squares fit adjustment in order to determine the recommended mass values and their uncertainties. All input data, including both the accepted and rejected ones, are tabulated and compared with the adjusted values obtained from the least-squares fit analysis. Differences with the previous Ame2016 evaluation are discussed and specific examples are presented for several nuclides that may be of interest to Ame users.     

The AME2016 atomic mass evaluation (Ⅱ).Tables,graphs and references

This paper is the second part of the new evaluation of atomic masses,AME2016.Using least-squares adjustments to all evaluated and accepted experimental data,described in Part Ⅰ,we derive tables with numerical values and graphs to replace those given in AME2012.The first table lists the recommended atomic mass values and their uncertainties.It is followed by a table of the influences of data on primary nuclides,a table of various reaction and decay energies,and finally,a series of graphs of separation and decay energies.The last section of this paper lists all references of the input data used in the AME2016 and the NUBASE2016 evaluations(first paper in this issue).     

The Ame2003 atomic mass evaluation: (I). Evaluation of input data,adjustment procedures

This paper is the first of two parts presenting the result of a new evaluation of atomic masses (Ame2003). In this first part we give full information on the used and rejected input data and on the procedures used in deriving the tables in the second part. We first describe the philosophy and procedures used in selecting nuclear-reaction, decay, and mass spectrometric results as input values in a least-squares evaluation of best values for atomic masses. The calculation procedures and particularities of the Ame are then described. All accepted data, and rejected ones with a reported precision still of interest, are presented in a table and compared there with the adjusted values. The differences with the earlier evaluation are briefly discussed and information is given of interest for the users of this Ame. The second paper for the Ame2003, last in this issue, gives a table of atomic masses, tables and graphs of derived quantities, and the list of references used in both this evaluation and the Nubase2003 table (first paper in this issue).Amdc: http://csnwww.in2p3.fr/AMDC/     

The Ame2020 atomic mass evaluation(II).Tables,graphs and references

This is the second part of the new evaluation of atomic masses,Ame2020.Using least-squares adjustments to all evaluated and accepted experimental data,described in Part I,we derived tables with numerical values and graphs which supersede those given in Ame2016.The first table presents the recommended atomic mass values and their uncertainties.It is followed by a table of the influences of data on primary nuclides,a table of various reaction and decay energies,and finally,a series of graphs of separation and decay energies.The last section of this paper provides all input data references that were used in the Ame2020 and the Nubase2020 evaluations.     

The NUBASE2016 evaluation of nuclear properties

This paper presents the NUBASE2016 evaluation that contains the recommended values for nuclear and decay properties of 3437 nuclides in their ground and excited isomeric(T_(1/2)≥100 ns) states.All nuclides for which any experimental information is known were considered.NUBASE2016 covers all data published by October 2016 in primary(journal articles) and secondary(mainly laboratory reports and conference proceedings) references,together with the corresponding bibliographical information.During the development of NUBASE2016,the data available in the "Evaluated Nuclear Structure Data File"(ENSDF) database were consulted and critically assessed for their validity and completeness.Furthermore,a large amount of new data and some older experimental results that were missing from ENSDF were compiled,evaluated and included in NUBASE2016.The atomic mass values were taken from the "Atomic Mass Evaluation"(AME2016,second and third parts of the present issue).In cases where no experimental data were available for a particular nuclide,trends in the behavior of specific properties in neighboring nuclides(TNN) were examined.This approach allowed to estimate values for a range of properties that are labeled in NUBASE2016 as "non-experimental"(flagged "#").Evaluation procedures and policies used during the development of this database are presented,together with a detailed table of recommended values and their uncertainties.     

The 1983 atomic mass evaluation: (IV). Evaluation of input values,adjustment procedures

This last paper in a series of four describes the philosophy and procedures in selecting nuclear-reaction and decay data and mass-spectrometric results as input for the calculation of best values for relative atomic masses. Both accepted and rejected data are presented in a table and there compared with the adjusted values.     

原子核质量的测量和评估

质量是原子核的基本性质之一,在核物理和核天体物理中都有重要的应用。原子核质量测量是目前核物理研究的一个前沿热点课题,国际上各个核物理实验室积极发展新设备和新技术,在短寿命放射性核素测量和超高精度质量测量方面取得了重要进展,本文对此进行了总结评述。在兰州重离子加速器冷却储存环（HIRFL-CSR）上利用等时性质量谱仪测量了一些原子核的质量,本文对其在测量精度、核态最短寿命等前沿进展做了简要介绍,并介绍了正在发展的双飞行时间质量谱仪。原子质量评估收集所有与原子核质量相关的实验数据,经过评估后推荐出质量值及相应误差。原子质量评估AME2016于2017年3月发表,为科技工作者提供基准数据。Mass is a fundamental property of the atomic nucleus. Nuclear mass data play an important role in nuclear physics and nuclear astrophysics. Thanks to the developments of novel mass spectrometers and radioactive nuclear beam facilities, the experimental knowledge of nuclear masses has been continuously expanding along two main directions, including:measurements aimed at high-precision mass values and at the most exotic nuclei far from the stability. The latest progress are reviewed in the paper. In the past few years, mass measurements of short-lived nuclides were performed using isochronous mass spectrometry based on the Cooler Storage Ring at the Heavy Ion Research Facility in Lanzhou(HIRFL-CSR). The progresses on the frontiers of short half-life and high precision are introduced. The Atomic Mass Evaluation (AME) is the most reliable source for the comprehensive information related to the atomic (nuclear) masses. The latest version of the AME, i.e., AME2016, was published in March, 2017, serving the research community with the benchmark data.     

The Evaluation of Atomic Masses

The ensemble of experimental data on the 2830 nuclides which have been observed since the beginning of Nuclear Physics are being evaluated, according to their nature, by different methods and by different groups. The two ‘horizontal’ evaluations in which I am involved: the Atomic Mass Evaluation AME and the NUBASE evaluation belong to the class of ‘static’ nuclear data. In this tutorial lecture I will explain and discuss in detail the philosophy, the strategies and the procedures used in the evaluation of atomic masses. This revised version was published online in July 2006 with corrections to the Cover Date.     

Released energy formula for proton radioactivity based on the liquid-drop model

In this work, based on the liquid-drop model and considering the shell correction, we propose a simple formula to calculate the released energy of proton radioactivity(Q_p). The parameters of this formula are obtained by fitting the experimental data of 29 nuclei with proton radioactivity from ground state. The standard deviation between the theoretical values and experimental ones is only 0.157 Me V. In addition, we extend this formula to calculate 51 proton radioactivity candidates in region 51≤Z≤83 taken from the latest evaluated atomic mass table AME2016 and compared with the Q_p calculated by WS4 and HFB-29. The calculated results indicate that the evaluation ability of this formula for Q_p is inferior to WS4 while better than HFB-29.     

Magnetic evaluation of advanced metal-evaporated tape in an advanced linear tape drive

Demand for increased data storage has resulted in the development of various types of magnetic tapes. To achieve higher recording density, tape manufacturers are developing thin-film tapes, such as advanced metal-evaporated (AME) tape, for use in linear tape drives. In recent studies, these new AME tapes have demonstrated sustainable mechanical durability at low tensions suitable for use in linear tape drives. An evaluation of the magnetic performance of these AME tapes including the impact of tape cupping and initial edge quality was the goal of this study. Head output, dropouts, head–tape interface friction, and lateral tape motion (LTM) were monitored throughout testing. As track widths continue to narrow, LTM has become one of the critical limitations of magnetic performance. To more accurately measure LTM during drive development, a new method involving the output voltage of a head-read element that has been adjusted to be halfway off the recorded track on tape was implemented (LTM_M). It is shown that positively cupped AME tapes will result in similar head output and fewer dropouts than the current MP tapes. The negatively cupped AME sample produced the lowest head output data and the highest amount of dropouts of all the tapes evaluated in this investigation. All the tapes evaluated demonstrated similar values of LTM when monitored at the center of the tape. When LTM was monitored at the lower edge of the tape, the positively cupped AME tape with the worst relative edge contour length resulted in the highest LTM_M. As found in previous studies, AME tapes produced slightly lower values of coefficient of friction than the MP tapes. From this investigation, positively cupped AME tapes with good initial relative edge contour length are recommended for use in linear tape drives, similar to those used in this study.     

Symmetry properties of radioactive N=Z nuclei

Recent mass measurements of proton-rich nuclei close to the N=Z line were used for the calculation of the interaction strength δV _pn between valence protons and neutrons. When compared with δV _pn values calculated from mass values of the AME’95 mass tables, the breaking down of the SU(4) symmetry is verified at Z=32,33,34.     

Mass measurements and evaluation around A = 22

Frequency ratio measurements with different combinations of the singly charged ions from ^{21, 22, 23}Na , ^{22, 24}Mg , and ^{37, 39}K were performed at the on-line Penning trap mass spectrometer ISOLTRAP, CERN, Geneva. The masses and mass differences were deduced with a relative uncertainty of about or even below one part in 10⁸ for the ions of interest using a least-squares analysis of all measured relations. The results have direct consequences for weak-interaction study as they give additional input to the test of CVC, and for nuclear astrophysics, because they help to establish the minimum observable signal for a NeNa cycle in a nova burst. We report here about the measurements and the detailed evaluation.     

Multivariate data analysis for depth resolved chemical classification and quantification of sulfur in SNMS

The quantification of elements in quadrupole based SNMS is hampered by superpositions of atomic and cluster signals. Moreover, the conventional SNMS data evaluation employs only atomic signals to determine elemental concentrations, which not allows any chemical specifications of the determined elements. Improvements in the elemental quantification and additional chemical information can be obtained from kinetic energy analysis and the inclusion of molecular signals into mass spectra evaluation. With the help of multivariate data analysis techniques, the combined information is used for the first time for a quantitative and chemically distinctive determination of sulfur. The kinetic energy analysis, used to solve the interference of sulfur with O₂ at masses 32-34 D, turned out to be highly important for the new type of evaluation.     

Assessment of interspecies scattering lengths a12 from stability of two-component Bose-Einstein condensates

A stability method is used to assess possible values of interspecies scattering lengths a12 in two-component Bose-Einstein condensates described within the Gross-Pitaevskii approximation. The technique, based on a recent stability analysis of solitonic excitations in two-component Bose-Einstein condensates, is applied to ninety combinations of atomic alkali pairs with given singlet and triplet intraspecies scattering lengths as input parameters. Results obtained for values of a12 are in a reasonable agreement with the few ones available in the literature and with those obtained from a Painlevé analysis of the coupled Gross-Pitaevskii equations.     

Examination of n-T_9 conditions required by N=50,82,126 waiting points in r-process

We examined the conditions of neutron density(n) and temperature(T_9) required for the N = 50, 82,and 126 isotopes to be waiting points(WP) in the r-process. The nuclear mass based on experimental data presented in the AME2020 database(AME and AME ±Δ) and that predicted using FRDM,WS4, DZ10, and KTUY models were employed in our estimations. We found that the conditions required by the N = 50 WP significantly overlap with those required by the N = 82 ones, except for the WS4 model. In addition, the upper(or lower) bounds of the n-T_9 conditions based on the models are different from each other due to the deviations in the two-neutron separation energies.The standard deviations in the nuclear mass of 108 isotopes in the three N = 50, 82, and 126 groups are about rms = 0.192 and 0.434 Me V for the pairs of KTUY-AME and WS4-KTUY models,respectively. We found that these mass uncertainties result in a large discrepancy in the nn-T_9 conditions, leading to significant differences in the conditions for simultaneously appearing all the three peaks in the r-process abundance. The newly updated FRDM and WS4 calculations can give the overall conditions for the appearance of all the peaks but vice versa for their old versions in a previous study. The change in the final r-process isotopic abundance due to the mass uncertainty is from a few factors to three orders of magnitude. Therefore, accurate nuclear masses of the r-process key nuclei, especially for ~(76) Fe,~(81)Cu,~(127)Rh,~(132)Cd,~(192)Dy, and ~(197)Tm, are highly recommended to be measured in radioactive-ion beam facilities for a better understanding of the r-process evolution.     

A simple method for the calculation of energy deposition profiles from range data of implanted ions

A rectangular approximation of the energy-loss function is used to calculate the initial range distribution of the energy deposited into atomic processes by ion implantation. It is required that range data and three values of the specific energy loss are taken from computed tables available in the literature. The resulting formula can be expressed by the error function and can easily be evaluated by means of an error-function table as well as by simple computation. For implantation into silicon, the results of the approximation differ by about 10% of the maximal energy deposition from the more precise calculations of Brice.     

A new determination of the 4 He and 3 He masses in a Penning trap

The atomic and nuclear masses of ⁴He and ³He have been measured using doubly charged ions in a Penning trap connected to an electron beam ion source. Recent technical improvements allow mass determinations with uncertainties of a few parts in 10¹⁰. The obtained atomic masses are 4.002 603 256 8(13) u and 3.016 029 323 5(28) u respectively. These values deviate by as much as 5 standard deviations from the accepted values. Received 23 October 2000 and Received in final form 6 February 2001     

High-accuracy mass determination of unstable cesium and barium isotopes

Direct mass measurements of short-lived Cs and Ba isotopes have been performed with the tandem Penning trap mass spectrometer ISOLTRAP installed at the on-line isotope separator ISOLDE at CERN. Typically, a mass resolving power of 600 000 and an accuracy of δm ≈ 13 keV have been obtained. The masses of ^123,124,126Ba and ^122mCs were measured for the first time. A least-squares adjustment has been performed and the experimental masses are compared with theoretical ones, particularly in the frame of a macroscopic-microscopic model.