This paper presents theoretical computations of the ionization rate of Rydberg lithium atom above the classical ionization threshold using semiclassical approximation. The yielded random pulse trains of the escape electrons are recorded as a function of emission time such that they can be related to the terms of the recurrence periods of the photoabsorption. This fact illustrates that it is ionic core scattering processes which give rise to chaos in autoionization dynamics and this is verified by comparison of our results with the hydrogen atom situation. In order to reveal the chaotic properties in detail, the sensitive dependence of the ionization rate upon the scaled energy is discussed for different scaled energies. This approach provides a simple explanation for the chaotic character in autoionization decay of Rydberg alkali-metal atoms.
The ionization rate of Rydberg lithium atoms in a static electric field is examined within semiclassical theory which involves scattering effects off the core.By semiclassical analysis,this ionization process can be considered as the promoted valence electrons escaping through the Stark saddle point into the ionization channels.The resulting escape spectrum of the ejected electrons demonstrates a remarkable irregular electron pulse train in time-dependence and a complicated nesting structure with respect to the initial launching angles.Based on the Poincaré map and homoclinic tangle approach,the chaotic behaviour along with its corresponding fractal self-similar structure of the ionization spectra are analysed in detail.Our work is significant for understanding the quantum-classical correspondence.
The chaotic behaviours of the Rydberg hydrogen atom near a metal surface are presented. A numerical comparison of Poincar′e surfaces of section with recurrence spectra for a few selected scaled energies indicates the correspondence between classical motion and quantum properties of an excited electron. Both results demonstrate that the scaled energy dominates sensitively the dynamical properties of system. There exists a critical scaled energy ε c , for ε < ε c , the system is near-integrable, and as the decrease of ε the spectrum is gradually rendered regular and finally turns into a pure Coulomb field situation. On the contrary, if ε > ε c , with the increase of ε, the system tends to be non-integrable, the ergodic motion in phase space presages that chaotic motion appears, and more and more electrons are adsorbed on the metal surface, thus the spectrum becomes gradually simple.
This paper presents recurrence spectra of highly excited lithium atoms with M=1 state in parallel electric and magnetic fields at a fixed scaled energy ε=0.03.Short-ranged potentials including ionic core potential and centrifugal barrier are taken into account.Their effects on the states and photo-absorption spectrum are analysed in detail.This demonstrates that the geometric features of classical orbits are of special importance for modulations of the spectral pattern.Thus the weak polarization as well as the reduction of correlation of electrons induced by short-ranged potentials give rise to the recurrence spectra of lithium M=1 atoms more compact than that of the M=0 one,which is in good agreement with the experimental prediction.
Based on the closed orbit theory framework together with the quantum defect the-ory and time-independent scattering matrices theory,we calculate the recurrence spectra of diamagnetic Cs atoms at several different scaled energies near the second ionization threshold.It is revealed that the new extra peaks in spectra are attributed to the combination recurrences of semiclassical closed orbits arising from core-scattered events.This method considers the dynamic states of the Rydberg electron in the core region and long-range region and can be analytically resumed to include all orders of core-scattering automatically.With this approach a convergent recurrence spectrum can be reasonably achieved.It is found that the spectral complexity depends highly sensitively on the scaled energy.With the in-crease of the scaled energy,the spectral structure changes from simple to com-plicate and the dynamic feature from regular to chaotic.The comparison of the re-currence spectra with Dando's result under the same conditions demonstrates that there exist some similarities and differences between them,and furthermore,the feasibility of the scattering matrix method is explained.
