Stability line

The origin of chemical elements has been explained by various nuclear synthesis routes, such as hydrogen or helium burning, and a-, e-, s-, r-, p- and x-processes. "Tc is believed to be synthesized by the s (slow)-process in stars. This process involves successive neutron capture and / decay at relatively low neutron densities neutron capture rates in this process are slow as compared to /1-decay rates. The nuclides near the -stability line are formed from the iron group to bismuth. 

Fig. 6.33 Similar to Fig. 6.31, but for ft = (Matsen 19956). In this case the Helmholtz free energy curve indicates that macrophase separation does not occur, and so an unbinding transition occurs at the composition indicated by the dot. In the phase diagram, the diamond shows where the stability line for microphase separation meets the unbinding transition (Lifshitz point). 

The IBM calculations use only two nuclear constituents, identical S and D bosons, or in the IBM-2, proton collective motion in a single formalism. Thus one might hope to be able to use the IBM to extrapolate from known properties of nuclei near the stability line to nuclei far from stability. The parameters are the total numbers of tt and v bosons, and Nv, and their one and two boson interactions. The usefulness of this theory for extrapolation depends on these parameters being Independent of N and Z, or known functions of N,Z. 

The analysis methods described here have highlighted some of the systematic features in the predictive properties of several of the commonly used atomic mass models. Additional understanding of these features and the availability of many new atomic masses for isotopes far from the stability line will serve as a basis for improving the models. The need clearly exists for a comprehensive revision and update of the mass predictions. A project, coordinated by the author, has been started to accomplish this. It is expected that new sets of mass predictions from a number of groups may be available late in 1986. 

KRU81]). The B strength function for nuclei along the decay back paths [coupled with neutron separation energies (Sn), fission barrier heights (Bf) and B"decay Q-values (Qg)] determines the amount of B delayed fission and neutron emission that occurs during the cascade back to the B stability line. 

The experimental study on rotational bands on JTT=0+ intruder states in the Pb isotopes is however more difficult than in Sn. In the first place the rotational bands in the neutron midshell nuclei of Sn could be studied by means of the (a,2n) reaction, whereas in Pb these nuclei are far away from the stability line. In the second place neutron Cij3/2 2 states angular... 

A crucial parameter in implanted source preparation is the total implant dose. For on-line work the flux of implant ions is very low as we are far from any stable beam. Even a flux of 106 ions s "1 gives only 1011 ions/day, well below the limiting concentration of order 0.1 atomic percent if implantation is at 50 KeV or above. A valuable feature of OLNO is that a sequence of isotopes may be simultaneously studied as the primary implant decays towards the stability line. This frequently makes accessible isotopes of elements which do not readily form ion beams. 

Proceedings of the International Symposium Why and How Should We Investigate Nuclides far off the Stability Line , Lysekil, Sweden, 21-27 August 1966, Arkiv Fysik 36, (1967). 

Figure 27 Schematic (a) Evans diagram and (b) corrosion potential vs. time behavior for localized corrosion stabilization. Line a on the Evans diagram represents the electrochemical behavior of the material before localized corrosion initiates, while line b represents the electrochemical behavior of the material in the localized corrosion site. Due to the low Tafel slope of the active site, the corrosion potential of the passive surface/local-ized corrosion site falls. If repassivation occurs, the anodic behavior reverts back to line a, and the corrosion potential increases again (line c). If repassivation does not occur, the corrosion potential will remain low (line d).

In a similar manner, one may also derive equations describing complex pe-pH stability diagrams for Fe-0-H20 at 25°C and 1 atm pressure involving gas, solution, and solid phases H2(g), 02(g), H20, Fe2+, Fe3+, Fe203, and Fe304 (Drever, 1982). In this case, stability lines can be drawn using the equations describing upper and lower boundary limits of H20 (referred to as step 1) as demonstrated above (Fig. 5.8). 

Figure 12.1. Stability lines for various metal-hydroxide species as a function of pH. The data were generated employing MINTEQA2 by assuming that pC02 = 0 and is in equilibrium with metal-hydroxide solids (from Evangelou, 1997, unpublished data, with permission).

The intersection of the complex stability lines at E (L) -0.15 V (Fig. 2.15) reveals a possible way into optimum bioindication, given the similarity of this value towards to that of many moderate-climate terrestrial plants (Table 2.7). But there can be some more general reasoning. 

Fig. 14. First-principles results for the surface energy of random and ordered surface alloys on Cu(lll). Cu2Pd and CusPd are Vs Vs nd (2x2) ordered alloys correspondingly. The dotted line is the stability line which is the surface energy of a disordered alloy with the maximal possible value of the SRO parameter for a given concentration.

It should be noticed, however, that the Ll2(lll)-A3B and [3 x 3 -A2B ordered structures are equally stable (on the same stability line) only if the effective interactions for more distant coordination shells are zero. If this is not the case, then the relative stability of these structures will depend on the value of the other interactions. The first difference actually appears at the second coordination shell in the surface layer (which corresponds to the third coordination shell in the bulk). The corresponding contribution from V) to the mixing energy of the Ll2(l 11)-A3B is again —3c, while it is zero in the... 

Shortly after Chadwick s discovery, a group of physicists in Rome, led by Enrico Eermi, began to stndy the interaction of nentrons with the nnclei of various elements. The experiments prodnced a nnmber of radioactive species, and it was evident that the absorption of a nentron increased the N Z ratio in target nuclei above the stability line (see Fig. 19.1). One of the targets nsed was nranium, the heaviest naturally occurring element. Several radioactive prodncts resnlted, none of which had chemical properties characteristic of the elements between Z = 86 (radon) and Z = 92 (uranium). It appeared to the Italian scientists in 1934 that several new transuranic elements (Z > 92) had been synthesized, and an active period of investigation followed. 

The purpose of these storage systems is to damp power fluctuations in the power grid to prevent computer crashes and equipment failure. Energy is stored in powerful electromagnets and can be retrieved whenever there is a need to stabilize line voltage during unanticipated disturbance in the power grid. 

---