Schedule Aug 03, 2006
Evolution and Scaling of an Intense Laser-Atom Interaction
Louis DiMauro (Ohio State Univ.)

Over the last decade, the tailoring of a light field for manipulating the dynamics of a system at the quantum level has taken a prevalent role in modern atomic, molecular and optical physics. As first described by Keldysh1, the ionization of an atom by an intense laser field will evolve depending upon the light characteristics and atomic binding energy. Numerous experiments have thoroughly investigated the dependence of the intensity and pulse duration on the ionization dynamics of inert gases. However, exploration of the wavelength dependence has been mainly limited to wavelengths ? 1 ?m or in the language of Keldysh to the multiphoton or mixed ionization regime. It is now technically possible to more thoroughly test scaling laws at longer mid-infrared wavelengths with the same sensitivity available at near-visible wavelengths. In addition, excitation with mid-infrared light augments the number of atomic systems which can be studied in the tunneling regime, as well as posing different model atomic structure, e.g. one- and two-electron like systems.

In this talk, we will discuss two topics. The first topic examines the long wavelength scaling of the strong field physics and its utility for experiments investigations. In the experiment alkali metal atom interact with an intense mid-infrared (3-4 ?m) laser field. In a Keldysh picture this scaled interaction should show similar ionization dynamics to the more familiar situation of a near visible light interacting with inert gas atoms. However, the interpretation of the spectra is greatly simplified since the alkali metal atoms are "good" one-electron like systems. Both ionization and harmonic processes are currently under investigation. The results show many similarities with the more extensively studied inert gas atom spectrum but significant differences do exist.

The second topic deals with inert gas atoms in large ponderomotive potentials. Both theoretical and experimental results will be presented that show neutral atoms experiencing nearly 400 eV of ponderomotive potential and ionization deep into the tunnel regime. These studies are fundamentally interesting but also provide a roadmap to light pulses that have both the atomic unit of time and length.

1. L.V. Keldysh, Sov. Phys. JETP 20, 1307 (1965).

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