Speaker
Prof.
Yang Sun
(Shanghai Jiao Tong University)
Description
Recent experimental advances have made it possible to study
spectroscopy in very heavy nuclei. It has been suggested [1] that by
studying the transfermium isotopes, in particular their excited
structure, one can gain useful information on relevant
single-particle states, which is the key to locating the anticipated
`island of stability'.
The study of rotation alignment of quasiparticles in superheavy
elements sensitively probes the single particle states of the high-
$j$ intruder orbits. These orbits are caused by the spin-orbit
interaction, which is ultimately linked to the question of energy
gaps in the single particle spectrum. We extend the applicability of
the Projected Shell Model (PSM) [2] to the transfermium region. We
study rotation alignment and the corresponding band-crossing
phenomenon in Cf, Fm, and No isotopic chains, and propose
observables to test the picture.
Isomeric states in very heavy nuclei are particularly interesting
because of their relatively long lifetimes. Xu {\it et al.}
suggested [3] that the occurrence of isomeric states can enhance the
stability of superheavy nuclei because the multi-quasiparticle
excitations decrease the probability for both fission and
$\alpha$-decay. Based on the successful PSM description for the
$^{254}$No isomers [1], we give a systematical prediction for
K-isomeric states in very heavy nuclei.
Knowledge on vibrational states is useful for this less known mass
region because of the interpretation of observed low-lying
spectroscopy. We further show that in very heavy nuclei collective
vibrations systematically appear as low-energy excitation modes [4].
We make a detailed prediction on $\gamma$-vibrational states and
their E2 transition probabilities to the ground state band in the
isotopes where active structure research is going on. Octupole
effects on single particle and collective motions will also be
discussed.
[1] R.-D. Herzberg {\it et al.}, Nature {\bf 442}, 896 (2006).
[2] K. Hara and Y. Sun, Int. J. Mod. Phys. E {\bf 4}, 637 (1995).
[3] F.-R. Xu {\it et al.}, Phys. Rev. Lett. {\bf 92}, 252501 (2004).
[4] Y. Sun {\it et al.}, submitted for publication.
Primary author
Prof.
Yang Sun
(Shanghai Jiao Tong University)
