Hydrogen ion
Inhaltsverzeichnis
Complete study of H2+ in intense laser fields
The movie shows the electronic density of H2+ as obtained in a complete NA-QMD study, i.e. taking into account all degrees of freedom (DOF) and simultaneously ionization and fragmentation [1-3].
Time-dependent electronic density
Movie:
An initially non-aligned H2+ is exposed to a horizontally polarized cw laser.
The electronic density and the dipole momentum (red point) are shown. Due to the induced dipole moment, the molecule rotates towards the laser polarization axis, fragments and ionizes.
For polyatomic many-electron systems a complete study means:
Taking into account all nuclear and electronic DOF and treating all fragmentation and ionization channels. However, such calculations are not available at present.
Alignment of H2+
Dimers exposed to high-intensity laser radiation show very different behaviour depending on the angle between the molecular axis and the electric field of the laser [4]. This is explained with two completely different mechanisms,
- Geometric alignment: The absorption of energy is enhanced for molecules parallel or nearly parallel to the field in comparison to the others.
- Dynamic alignment: The laser couples to the permanent or induced dipole moment of the non-oriented molecules and thus generates an effective torque towards the laser axis.
In the movies shown below the vertical polarized laser is indicated by a white background color.
Laser-induced rotation of H2+
![h2+ rotation](https://tu-dresden.de/mn/physik/itp/tam/ressourcen/bilder/h2-_rot.png/@@images/fbb3ac92-2b16-4756-89b7-4e2397c48017.png)
H2+ is exposed to a laser pulse with a wavelength of 266 nm, a pulse duration of 500 fs and an intensity of 6e13 W/cm^2.
Movie:
The molecule is turned to the laser axis. When the laser peaks, it is oscillating around the laser axis. After the laser pulse, it is freely rotating.
Dynamical alignment of H2+
![h2+ alignment](https://tu-dresden.de/mn/physik/itp/tam/ressourcen/bilder/h2-_al.png/@@images/9e476ed7-4821-4b68-ab90-48f0f6968c1d.png)
H2+ is exposed to a laser pulse with a wavelength of 266 nm, a pulse duration of 200 fs and an intensity of 1.2e14 W/cm^2.
Movie:
The molecule rotates towards the laser axis and fragments. Thus, strongly aligned fragments result.
- M. Fischer, J. Handt, J.-M. Rost, F. Grossmann, and R. Schmidt, Molecular rotation in strong-field ionization, Phys. Rev. A 86, 053821 (2012).
- J. Handt, S. M. Krause, J. M. Rost, M. Fischer, F. Grossmann, and R. Schmidt,
Complete dynamics of H2+ in intense laser fields, (arXiv:1103.1565v2 [physics.atm-clus]) (2011). - M. Uhlmann, T. Kunert, F. Grossmann, and R. Schmidt,
Mixed classical-quantum approach to excitation, ionization, and fragmentation of H2+ in intense laser fields, Phys. Rev. A 67, 013413 (2003). - M. Uhlmann, T. Kunert, and R. Schmidt, Molecular alignment of fragmenting H2+ and H2 in strong laser fields, Phys. Rev. A 72, 045402 (2005).