Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Isomeric states, shell model

The odd-neutron nuclei close to the N = 82 neutron-shell closure are shown to be well described by available shell-model neutron states. The N = 81 isotones below the shell closure exhibit 1 = 3/2 ground states in the elements up to samarium (Z = 62), where there is a change to I = 1/2 ground states. This behaviour is explained by the lowering of the Sj shell-mo l state with respect to dj with increasing proton number. The 1 = 11/2 isomeric states in the full range are due to h,. The measured moments also support the assignments above. [Pg.369]

Strutinsky developed an extension of the liquid drop model which satisfactorily explains the fission isomers and asymmetric fission. For such short half-lives the barrier must be only 2-3 MeV. Noting the manner in which the shell model levels vary with deformation ( 11.5, the "Nilsson levels"), Strutinsky added shell corrections to the basic liquid-drop model and obtained the "double-well" potential energy curve in Figure 14.14b. In the first well the nucleus is a spheroid with the major axis about 25 % larger than the minor. In the second well, the deformation is much larger, the axis ratio being about 1.8. A nucleus in the second well is metastable (i.e. in isomeric state) as it is unstable to y-decay to the first well or to fission. Fission from the second well is hindered by a 2 - 3 MeV barrier, while from the first well the barrier is 5 - 6 MeV, accounting for the difference in half-lives. [Pg.386]

When the fission isomeric states were discovered (Polikhanov et al. 1962), it became clear that the fission potential should have a second minimum as a function of the deformation and the observed fission isomers are shape isomers in such a second minimum. Strutinsky s proposal (see O Chap. 2 in this Volume) was to combine the virtues of both the LDM and shell models to describe such a second minimum of the fission potential. [Pg.284]

Figure 3 Fraaional population decay curves for a model of three-state molecular isomerization with all trajectories initially distributed uniformly on the constant-energy shell within a single isomer... Figure 3 Fraaional population decay curves for a model of three-state molecular isomerization with all trajectories initially distributed uniformly on the constant-energy shell within a single isomer...

See other pages where Isomeric states, shell model is mentioned: [Pg.148]    [Pg.399]    [Pg.65]    [Pg.134]    [Pg.118]    [Pg.84]    [Pg.440]    [Pg.173]    [Pg.327]    [Pg.173]    [Pg.935]    [Pg.283]    [Pg.379]    [Pg.1181]    [Pg.344]   
See also in sourсe #XX -- [ Pg.149 ]




SEARCH



Isomeric state models

Isomeric states

Shell model

Shell-model states

© 2024 chempedia.info