Towards new understanding of nuclear rotation

Properties of time evolution of wave packets built up from rotator eigenstates are discussed. The mechanism of perfect cloning of the initial wave packet for "circular states" at fractional revival times is explained. The smooth transition from "circular" to "linear" through intermediate "elliptic" is described. Example of time evolution of a nuclear wave packet created in Coulomb excitation mechanism is presented.Comment: 4 pages, 2 figures, LaTeX (appb.sty included), Presented at the XXXIII Zakopane School of Physics, Zakopane, Poland, September 1-9, 1998. To appear in Acta Phys. Polon. B (1999

Geometrical properties of intelligent spin states and time evolution of coherent states

We remind the properties of the intelligent (and quasi-intelligent) spin states introduced by Aragone et al. We use these states to construct families of coherent wave packets on the sphere and we sketch the time evolution of these wave packets for a rigid body molecule.Comment: 7 pages + 4 figures (11p), LaTeX2e, Paper accepted for publication in J.Phys.A: Math.Ge

Stability and instability of a hot and dilute nuclear droplet

The diabatic approach to collective nuclear motion is reformulated in the local-density approximation in order to treat the normal modes of a spherical nuclear droplet analytically. In a first application the adiabatic isoscalar modes are studied and results for the eigenvalues of compressional (bulk) and pure surface modes are presented as function of density and temperature inside the droplet, as well as for different mass numbers and for soft and stiff equations of state. We find that the region of bulk instabilities (spinodal regime) is substantially smaller for nuclear droplets than for infinite nuclear matter. For small densities below 30% of normal nuclear matter density and for temperatures below 5 MeV all relevant bulk modes become unstable with the same growth rates. The surface modes have a larger spinodal region, reaching out to densities and temperatures way beyond the spinodal line for bulk instabilities. Essential experimental features of multifragmentation, like fragmentation temperatures and fragment-mass distributions (in particular the power-law behavior) are consistent with the instability properties of an expanding nuclear droplet, and hence with a dynamical fragmentation process within the spinodal regime of bulk and surface modes (spinodal decomposition).Comment: 17 pages, 11 figures, LaTeX2e, EPJA style (included

Instabilities of a hot expanded nuclear droplet

The stability of hot expanded nuclear droplets against small bulk and surface oscillations is examined and possible consequences for multifragmentation are discussed.Comment: LaTeX (uses epsfig.sty), 6 pages with 6 eps figures inside text. Talk given at XXVII International Workshop on Gross Properties of Nuclei and Nuclear Excitations, "MULTIFRAGMENTATION", Hirschegg, January 17--23, 199

New mechanism of collapse and revival in wave packet dynamics due to spin-orbit interaction

The article discusses the properties of time evolution of wave packets in a few systems. Dynamics of wave packet motion for Rydberg atoms with the hierarchy of collapses and revivals is briefly reviewed. The main part of the paper focuses on the new mechanism of quantum reccurrences in wave packet dynamics. This mechanism can occur (in principle) in any physical system with strong enough spin-orbit interaction. We discuss here the SPIN_ORBIT PENDULUM effect that consists in different motions of subpackets possessing different spin fields and results in oscillations of a fraction of average angular momentum between spin and ordinary subspaces. The evolution of localized wave packet into toroidal objects and backwards (for other class of initial conditions) is also subject to discussion.Comment: 10 pages, LaTeX, 7 PS figures (in 6 separate files), to appear in Acta Phys. Polon. (Invited lecture at XXXI Zakopane School of Physics, Zakopane, Poland, September 3-11, 1996

Pictures of quantum nuclear rotation beyond the correspondence principle

We analyze the time evolution of simple nuclear rotational wave packets (WP) called circular, linear or elliptic assuming that rotational energies are proportional to I(I+1). The scenario of fractional revivals found by Averbukh and Perelman is adapted to symmetric WP and compared to that which holds for asymmetric WP. In both cases various shapes are identified under these lines in particular many cases of cloning. 'Mutants' WP are found most often