in Quantum Electronics
Henry Baltes, Peter Günter, Ursula Keller,
Fritz K. Kneubühl †, Walter Lukosz,
Hans Melchior, Markus W. Sigrist
Adrian Nikolaus Pfeiffer
Attosecond Electron Kinematics in
Strong Field Single and Double Ionization
1st edition 2011.
XVIII, 102 pages, € 64,00.
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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