Eur. Phys. J. D 4, 73-81 (1998)
https://doi.org/10.1007/s100530050186

Creation and manipulation of coherences in molecules with a pulsed magnetic field

Physikalisch-Chemisches Institut der Universität Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland

Corresponding author: ^a jrhuber@pci.unizh.ch

Received: 8 April 1998
Accepted: 3 June 1998
Published online: 15 October 1998

Abstract

We demonstrate the application of a pulsed magnetic field for the creation and manipulation of coherences in molecular systems, using quantum beat spectroscopy for the detection of the dynamics of the molecular superposition states. In all cases, the experiments are performed on energy levels in electronically excited states of the (jet-cooled) CS₂ molecule populated by a short laser pulse. In the basic experiment, following excitation of initially degenerate Zeeman sublevels under zero field conditions with suitable laser polarization, quantum beats are generated at the moment the magnetic field is switched on, even when the field is delayed by several excited state lifetimes. By quenching of the field, it is shown that the molecule may be "frozen" in any superposition state of the participating sublevels. Using a combination of static and pulsed fields with different orientations, the molecule can be prepared in a more general state, described by coherences among all Zeeman substrates. This is achieved by choosing an appropriate time delay for the switched field, without any change to the geometrical parameters of the experiment such as laser polarization or detection direction. Numerical simulations of these dynamical coherence phenomena have been performed to support assignment and interpretation of the experimental results.