Mass excess

Wapstra and Audi [22] evaluated the experimental data on masses as well as reaction and decay energies to obtain a consistent set of atomic masses m. The values for the isotopes of the Pt group (in atomic mass units u = (1.660566+0.000009) x 10 kg) are listed in Table 1/1, p. 2, and Table 1/2, p. 4. Also the mass excess values Am for the neutral atoms (Am (in keV) = (m—A) 931501.6) are given. The data, which were derived from empirical systematic trends [24], are marked by an asterisk. 

Throughout this chapter the uncertainties of the data are given in the parentheses which follow the listed data. These uncertainties refer always to the last digits of the values, e.g., 1074.5(17) means 1074.5 + 1.7 (see also p. 30). 

Most of the mass formulas mentioned include the effect of nuclear deformation explicitly. Accordingly, values for the equilibrium deformation in the ground state, radial proton and/or neutron distribution as well as quadrupole moments were deduced from the mass calculations. The values agree in general quite well with experimental results [32, 33, 35]. 

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G. W. C. Kaye and T. H. Laby, Tables of Physical and Chemical Constants, Longman 1995, gives a table of properties of the nuclides including isotopic abundance or half-life, decay modes, mass excess, neutron capture cross-section and ground-state spin and parity. This publication, with a prospect of regular updates, is available on the website http //www.kayelaby.npl.co.uk/. 

Neutron mass excess 8.07144 MeV neutron spin 1/2 H atom mass excess 7.288 99 MeV proton spin 1/2... 

Estimate the amount of energy generated when a carbon white dwarf with the mass of the Sun is incinerated to 56Ni (mass excess —53.9 MeV) and compare it with the energy needed to disrupt the star if its radius is 5000 km and its density assumed uniform. (IMeV = 1.6 x 10 6erg G = 6.67 x 10-8 dyncm2gm-2.)... 

A 1. Symbol for application of heat in a reaction (e.g., A -A P). 2. Symbol for change. 3. In organic structures, used to denote the presence of a double bond, usually with a superscript number to indicate position. 4. Symbol for mass excess. 

The most carefully studied element is the simplest, hydrogen, which has a natural atomic mass (1.0080) slightly greater than that of a single proton (1.0078). (SeeTable 3-4.) This mass excess is only 0.0002 atomic mass units, but the investigation of this excess revealed the 3 isotopes of that element. 

That is, the concentration in the crystal is the same as that in the initial melt at steady state. Therefore, the growth of the crystal does not affect the mass excess or deficiency in the melt anymore, meaning that the concentration profile (in interface-fixed reference frame) in the melt is at steady state. Steady state maybe reached only for elements whose concentration in a mineral can vary non-stoichiometrically. 

The mass defect (mass excess) or of a nucleus is equivalent to the binding energy of the nucleons in the nucleus and corresponds to ... 

MASS DEFECT. The difference A between the atomic number A and the atomic mass M of a nuclide. A = A - M. The negative of the mass defect. —A. is known as the mass excess. 

In many tabulations of nuclear properties, such as that in Appendix B, the quantity that is tabulated is the mass excess or mass defect rather than the mass. The mass excess, A, is defined as M(A, Z) — A, usually given in units of the energy equivalent of mass. Since in most, if not all calculations, the number of nucleons will remain constant, the use of mass excesses in the calculations will introduce an arithmetic simplification. Another term that is sometimes used is the mass excess per nucleon or the packing fraction [=(M — A)/A]. 

Figure 2.6 Mass excesses of the known nuclei with A = 111.

Figure 2.8 Plot of the nuclear mass excesses vs. neutron number N and atomic number Z for the light nuclei showing the nuclear mass surface and the valley of [3 stability from Halliday, et al., 1992 reprinted by permission of John Wiley Sons, Inc.

C, 2 hr, 20 % KOH of the mass, excess C2H2 under a pressure of 16 atm. From reference (78ZOR1733). See also Scheme 1. h From GLC data. 

Be is not a stable isotope despite its large neutron separation energy, because it can beta decay to the more stable isobar 7Li (see under Mass excess in Glossary). As a resultno 7Be exists on Earth or in the meteorites, except by transient production by cosmic rays, and none has been seen (yet) in stars. But it is stable against breaking up into nuclear particles (as opposed to beta decay) and is an observable isotope in nature in two ways. 

When He fuses in the hydrogen-exhausted core at the center of a star, itliberates more nuclear power by making l60 than by making 12C, as the smaller atomic mass excess for l60 reveals. The relative amounts of 12C and l60 made during He burning depend on the rate ofthe nuclear reaction12 C + 4He l60. The quantum probability for this reaction to occur has been very hard to pin down. Its precise value is very... 

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