Heidelberg 1999 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
A: Atomphysik
A 14: Poster
A 14.30: Poster
Donnerstag, 18. März 1999, 16:30–19:00, PY
Laser induced resonance trapping in atoms — •A.I. Magunov1,2, I. Rotter2,3, and S.I. Strakhova4 — 1General Physics Institute, Russian Academy of Sciences, 117942 Moscow, Russia — 2Max-Planck-Institut fuer Physik komplexer Systeme, 01187 Dresden — 3Technische Universitaet, Institut fuer Theoretische Physik, 01062 Dresden — 4Mocow State University, Institute of Nuclear Physics, 119899 Moscow, Russia
The motion of the complex energies of two autoionizing states or of a discrete and an autoionizing state in an atom, driven by a strong laser field, are traced as a function of the field strength for different field frequencies and atomic parameters. The corresponding variation of the photoionization cross section is studied. The ratio between direct coupling of the states and their coupling via a continuum defines the Fano parameter Q. The investigations are performed analytically and illustrated by numerical results for the case of two states coupled to one common continuum. Most interesting is the critical region where a crossing of the trajectories occurs. The crossing is usually avoided with the only exception that the conditions for meeting a double pole of the S-matrix are fulfilled, i.e. laser induced degenerate states are formed. At this critical field intensity, level repulsion in the complex plane occurs. When the resonances are coupled mainly via the continuum (small Q value), resonance trapping dominates, i.e. a short and a long lived resonance state are formed. When, however, the direct coupling dominates (large Q value), level repulsion along the real axis takes place. Population trapping (defined by a vanishing decay width of one of the states) results from the interplay of the direct coupling of the states and their coupling via the continuum. For Q ≈ 1, it appears at a field intensity not much larger than the critical. Numerical results for concrete atoms will be given.