scholarly journals Deformation and shell effects in nuclear mass formulas

2012 ◽  
Vol 874 ◽  
pp. 81-97 ◽  
Author(s):  
César Barbero ◽  
Jorge G. Hirsch ◽  
Alejandro E. Mariano
Keyword(s):  
Nuclear Mass ◽  
Shell Effects ◽  
Mass Formulas

scholarly journals Least-squares fitting applied to nuclear mass formulas. Solution by the Gauss–Seidel method

2021 ◽  
Author(s):  
B. Mohammed-Azizi ◽  
H. Mouloudj
Keyword(s):  
Linear System ◽  
Least Squares ◽  
Statistical Data ◽  
Large Data ◽  
Positive Definite ◽  
Nuclear Mass ◽  
Positive Definite Matrices ◽  
Seidel Method ◽  
Semi Empirical ◽  
Mass Formulas

In this paper, a numerical method optimizing the coefficients of the semi empirical mass formula or those of similar mass formulas is presented. The optimization is based on the least-squares adjustments method and leads to the resolution of a linear system which is solved by iterations according to the Gauss–Seidel scheme. The steps of the algorithm are given in detail. In practice, the method is very simple to implement and is able to treat large data in a very fast way. In fact, although this method has been illustrated here by specific examples, it can be applied without difficulty to any experimental or statistical data of the same type, i.e. those leading to linear system characterized by symmetric and positive-definite matrices.

Further study on nuclear mass formulas

1980 ◽  
Vol 334 (3) ◽  
pp. 470-476 ◽  
Author(s):  
C.Y. Tseng ◽  
T.S. Cheng ◽  
F.C. Yang
Keyword(s):  
Nuclear Mass ◽  
Mass Formulas

Nuclear mass formulas for astrophysics

2006 ◽  
Vol 777 ◽  
pp. 623-644 ◽  
Author(s):  
J.M. Pearson ◽  
S. Goriely
Keyword(s):  
Nuclear Mass ◽  
Mass Formulas

SEARCH FOR CORRELATIONS OF MOST PROBABLE NUCLEAR CHARGE ZP OF PRIMARY FISSION FRAGMENTS WITH COMPOSITION AND EXCITATION ENERGY

1961 ◽  
Vol 39 (3) ◽  
pp. 646-663 ◽  
Author(s):  
Charles D. Coryell ◽  
Morton Kaplan ◽  
Richard D. Fink
Keyword(s):  
Fine Structure ◽  
Nuclear Charge ◽  
Low Energy ◽  
Charge Ratio ◽  
Nuclear Chemistry ◽  
Fission Process ◽  
Shell Effects ◽  
Crude Approximation ◽  
Charge Displacement ◽  
Mass Formulas

The repartition of nuclear charge in fission has a narrower dispersion than almost any other property connected with the fission process. To a crude approximation, the distribution of nuclear charge between light and heavy partners L and H leads to the most probable charges (Zp)L and (ZP)H displaced from the respective charges ZA of β-stability by the same amount for the two fragments (Glendenin rule of equal charge displacement ECD, 1946). The existence of shell offsets in the ZA vs. A function for different neutron- and proton-shell regions must be considered. All available data for thermal fission U235(nth,F) are examined critically. The data show sudden offset-like drifts (fine structure) that may well be associated with shell properties of the products before the "neck" has dissolved. It is shown that these data eliminate naive equal charge displacement ECD, also an older competitive prescription of constant charge ratio CCR for the products, and an empirical Russian prescription (Apalin etal., 1960). The data are also examined in the light of the postulate that fission gives minimum nuclear plus coulombic potential energy (Present 1947, Fong 1955, Swiatecki-Blann 1960), and it is shown that the present mass formulas give too much uncertainty three to four β-decays from stability to give a useful test, but that shell effects in masses must be retained. Data from charged-particle fission with energy deposit up to 40–50 Mev are in reasonable accord with the low-energy data on correcting for composition and neutron boil-off. It is concluded from experiment that ZP is a single-valued function of A, known to about ± 0.15 unit for low-energy fission and ± 0.25 unit for medium-energy fission, and that the fine structure very probably present is an indication of intrinsic nuclear chemistry.

scholarly journals Nuclear mass measurements with radioactive ion beams

2019 ◽  
Vol 28 (04) ◽  
pp. 1930005 ◽  
Author(s):  
Michael A. Famiano
Keyword(s):  
Mass Measurement ◽  
Measurement Techniques ◽  
Nuclear Mass ◽  
Mass Measurements ◽  
Future Directions ◽  
Advantages And Disadvantages ◽  
Nuclear Masses ◽  
Under Construction ◽  
Very High ◽  
Practical Constraints

Nuclear masses are the most fundamental of all nuclear properties, yet they can provide a wealth of knowledge, including information on astrophysical sites, constraints on existing theory, and fundamental symmetries. In nearly all applications, it is necessary to measure nuclear masses with very high precision. As mass measurements push to more short-lived and more massive nuclei, the practical constraints on mass measurement techniques become more exacting. Various techniques used to measure nuclear masses, including their advantages and disadvantages are described. Descriptions of some of the world facilities at which the nuclear mass measurements are performed are given, and brief summaries of planned facilities are presented. Future directions are mentioned, and conclusions are presented which provide a possible outlook and emphasis on upcoming plans for nuclear mass measurements at existing facilities, those under construction, and those being planned.

scholarly journals Electromigration-induced directional steps towards the formation of single atomic Ag contacts

2020 ◽  
Vol 11 ◽  
pp. 680-687
Author(s):  
Atasi Chatterjee ◽  
Christoph Tegenkamp ◽  
Herbert Pfnür
Keyword(s):  
Fourier Transforms ◽  
Single Point ◽  
Point Contact ◽  
Single Atom ◽  
Point Contacts ◽  
Cross Sectional ◽  
Shell Effects ◽  
Theoretical Approaches ◽  
Average Grain Size ◽  
Thinning Process

Even though there have been many experimental attempts and theoretical approaches to understand the process of electromigration (EM), it has not been quantitatively understood for ultrathin structures and at grain boundaries. Nevertheless, we showed recently that it can be used reliably for the formation of single atomic point contacts after careful pre-structuring of the initial Ag nanostructures. The process of formation of nanocontacts by EM down to a single-atom point contact was investigated for ultrathin (5 nm) Ag structures at 100 K by measuring the conductance as a function of the time during EM. In this paper, we compare the process of thinning by EM of structures with constrictions below the average grain size of Ag layers (15 nm) with that of structures with much larger initial constrictions of around 150 nm having multiple grains at the centre constriction prior to the formation of a point contact. Even though clear morphological differences exist between both types of structures, quantized conductance plateaus showing the formation of single point contacts have been observed for both. Here we put emphasis on the thinning process by EM, just before a point contact is formed. To understand this thinning process, the semi-classical regime before the contact reaches the quantum regime was analyzed in detail. For this purpose, we used experimental conductance histograms in the range between 2G 0 and 15G 0 and their corresponding Fourier transforms (FTs). The FT analysis of the conductance histograms exhibits a clear preference for thinning along the [100] direction. Using well-established models, both atom-by-atom steps and ranges of stability, presumably caused by electronic shell effects, can be discriminated. Although the directional motion of atoms during EM leads to specific properties such as the instabilities mentioned, similarities to mechanically opened contacts with respect to cross-sectional stability were found.

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