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Series in Quantum Electronics
edited by
Henry Baltes, Peter Günter, Ursula Keller,
Fritz K. Kneubühl †, Walter Lukosz,
Hans Melchior, Markus W. Sigrist
Vol. 53
Adrian
Nikolaus Pfeiffer
Attosecond Electron Kinematics in
Strong Field Single and Double Ionization
1st
edition 2011. XVIII, 102 pages, € 64,00.
ISBN 978-3-86628-386-2
The key
process underlying attosecond physics is strong field ionization by femtosecond
laser pulses. The model that has been established to describe this process is a semi-classical model in which the electron escapes from
the atom by tunneling and moves afterwards on a classical trajectory.
Currently, the frontiers in attosecond physics are moving forward, pushing
resolution in time and space. This raises the demand for precision in the
semi-classical model.
In this work the electron kinematics following
tunnel ionization are investigated by COLTRIMS (COLd Target Recoil Ion Momentum
Spectroscopy). Conclusions are presented concerning the initial conditions of
the electron trajectory, the starting time of the electron trajectory, and
kinematic correlations of the electrons in double ionization.
The
force exerted by the laser field dominates the trajectory of the electron, but
the Coulomb interaction with the parent ion induces subtle effects. It is found
that these effects can be used as a probe for the initial conditions of the
electron trajectory. The TIPIS model is introduced for the calculation of the
exit of the tunnel, demonstrating that multi-electron effects and the Stark
shift play a critical role.
Surprising
results are found in the case of strong field double ionization. A mechanism
that dominates double ionization by linearly polarized laser pulses over a wide
intensity regime is recollision of the first emitted electron with its parent
ion. By using close-to-circularly polarized laser pulses this mechanism is
avoided. Nevertheless, intensity dependent correlations between the emission
directions of the two electrons are found. Furthermore, the ionization times of
the first and the second ionization step are measured with the attoclock
technique. It is found that the ionization time of the second electron is
earlier than predicted. These results are incompatible with the semi-classical
model in the independent-electron approximation.
About
the author:
Adrian Pfeiffer studied physics in Freiburg, London
and Heidelberg. After receiving his diploma degree from Heidelberg University
in 2006 he joined the Institute of Quantum Electronics at the Swiss Federal
Institute of Technology (ETH) in Zurich. His research focused on strong field
laser physics and attoscience.
Keywords:
Laser, strong field laser physics, attoscience, ionization
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