Berlin 2001 – wissenschaftliches Programm

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A: Atomphysik

A 18: Photoionisation II (joint session A and MO)

A 18.1: Vortrag

Freitag, 6. April 2001, 15:45–16:00, H1012

Photodetachment microscopy in electric and weak magnetic fields — •Tobias Kramer, Christian Bracher, and Manfred Kleber — Physik–Department, TU München, 85747 Garching

We study near-threshold photodetachment from negative ions in the presence of static electric and magnetic fields that are uniform and parallel. The static electric field serves to guide the electrons, released by a laser beam from the ions, over a macroscopic distance to a position-sensitive spectrometer. There, electron interference will occur, giving rise to intensity fringes that reflect the nodes and antinodes of the electronic wave function. In that respect the setup is a microscope that records the spatial density of the photoelectrons. The experimental results by Blondel et al. are in perfect agreement with theory.

The inclusion of a magnetic field parallel to the electric field will cause circular motion in the plane perpendicular to the fields. We show that the magnetic field focuses the photoelectrons in a constriction pattern that repeats itself spatially. There, interference of four classical paths will occur. In addition, a quantum regime exists that is governed by the uncertainty principles.