Effect of the Rydberg states on the time evolution of nonstationary states below or just above the ionization threshold

Journal Article · Thu Sep 15 04:00:00 EDT 2005 · Physical Review. A

DOI:https://doi.org/10.1103/PhysRevA.72.032716· OSTI ID:20718554

Komninos, Yannis ^[1]; Nicolaides, Cleanthes A ^[1]

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1. Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vasileos Constantinou Avenue, Athens 11635 (Greece)

We consider problems of short-time dynamics of a polyelectronic atomic nonstationary state, V, assumed to be formed as a wave packet at t=0. We focus on two cases, for which the role of the quasicontinuum of the upper part of the Rydberg states, with which the V state has nonzero coupling matrix elements, is investigated. In the first case, the position of the V state is just above the ionization threshold, E=0, and so V dissipates into the free electron continuum as an autoionizing state. The question is how the presence of the Rydberg series converging to E=0 affects the time evolution of the autoionizing V. In the second case, the position of V is embedded in the quasicontinuum of the Rydberg series below threshold. The question is whether there are distinct features in the time evolution of this V, although its position is in the discrete part of the energy spectrum. In this case, by focusing on short times and by evaluating analytically certain infinite sums, analogous to Fourier integrations, the following result is obtained: For small times, the V state evolves as an exponentially decaying state. However, in addition to the term describing exponential decay, there is a term, entering with a small coefficient, which describes exponential growth and eventually dominates. It is shown that exponential decay holds for times shorter than the time t{sub p} needed by the wave packet to reach the outer classical turning point. For the decay to be physically meaningful, this time must be smaller than the time t{sub d} which equals the inverse of the half-width in atomic units. We examined a model system of V-Rydberg state interaction based on the Boron {sup 2}S spectrum. The results indicate that the effect is observable on the scale of femtoseconds.

• OSTI ID: 20718554
• Journal Information: Physical Review. A, Journal Name: Physical Review. A Journal Issue: 3 Vol. 72; ISSN 1050-2947; ISSN PLRAAN
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
AUTOIONIZATION
BORON
COUPLING
DECAY
ELECTRONS
ENERGY SPECTRA
EVOLUTION
MATRIX ELEMENTS
PHOTON-ATOM COLLISIONS
RYDBERG STATES
WAVE PACKETS