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A: Atomphysik

A 11: Photoionisation I

A 11.2: Talk

Tuesday, March 23, 2004, 16:45–17:00, HS 132

Ionisation by very short intense laser pulses — •Darko Dimitrovski and John S Briggs — Theoretische Quantendynamik, Universität Freiburg

We investigate ionisation and excitation of H(1s) in the limit of very short electric field pulses, analytically and numerically and both in the limit of small and extremely large peak electric fields. A fully 3D numerical code based on the discrete variable representation is used for verification of the analytic results.

In the limit of small peak fields, and for a few-cycle laser pulse, the total ionisation and excitation probabilities, as well as the momentum distribution can be described well by first order time dependent perturbation theory. The energy distribution as a result of such pulses shows a peaked structure and depends on the shape of the carrier. Additionally, a method for measuring the relative carrier-envelope phase is proposed.

For a half-cycle pulse, the results for the population probabilities depend only on the momentum transferred by the field and not on the pulse shape. For a one-cycle pulse and in the limit of very high momentum transfer (when the atom is completely ionised after the first half cycle) an asymptotic analytical expression for the ground state probability is obtained. In this case the ground state probability depends on both the momentum transferred by the field and the period of the pulse but not on the pulse shape.