Laser Excited Atoms and Molecules

At beamline I411 we study the electronic structure of atoms and molecules by analyzing the photo electrons after ionization with soft x-ray radiation. Detecing the direct emission of photo electrons gives insight into the structure of the electron shell in the ground state. In molecules these spectra already contain information about the binding properties. For getting further insight into the dynamics of the multi electron systems the decay of the atoms and molecules after resonant or non-resonant excitation can be studied.

With the tunable laser system at beamline I411 it is possible to pump atoms and molecules into excited states. The possibility to study these excited states give rise to several new types of experiments:

• The influence of changes in the outer electron shells on deeper lying states can be studied. This is of particular interest if atomic spectra shall be compared to solid state spectra where the outer electrons are taking part in the binding.

• Due to the polarization of laser light the excited state is spacially or magnetically aligned. This gives the possibility to examine the angular distribution of photoelectrons in more detail then it is possible with not aligned samples.

• Molecules can be excited into dissociating states. The photoelectron spectra of these molecules should reveal information on the details of the dissociation process.

• Continuous wave lasers have an extremly high spectral resolution compared with soft x-ray radiation. This opens up the possibility to select specific states by the laser excitation. The laser excited state can be selected to be of a well defined atomic state. Molecules with a specific vibrational and rotational state can be selected.

• Photoelectron spectroscopy on excited states can be a test field for theories concerning the electronic structure of atoms and molecules. States of matter that normally exist only und very high temerature can be produced in a controlled way.

Publications

J. Schulz, M. Tchaplyguine, T. Rander, O. Björneholm, S. Svensson, R. Sankari, S. Heinäsmäki, H. Aksela, S. Aksela, and E. Kukk
Shakedown in core photoelectron spectra from aligned laser-excited Na atoms
Physical Review A 72, 010702 (2005)

J. Schulz, M. Tchaplyguine, T. Rander, H. Bergersen, A. Lindblad, G. Öhrwall, S. Svensson, S. Heinäsmäki, R. Sankari, S. Osmekhin, S. Aksela, and H. Aksela
Final state selection in the 4p photoemission of Rb by combining laser spectroscopy with soft-x-ray photoionization
Physical Review A 72, 032718 (2005)