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A Penning trap experiment for studies with atoms and ions in extreme laser fields
According to Albert Einstein (photoelectric effect 1905), the number of photoelectrons emitted from matter is proportional to the light intensity. In our experiment, we study the highly non-linear process of multiphoton ionisation, where an atom or molecule absorbs many photons in one step. This non-linear process is a hot topic in laser research.
The interaction of highly intense radiation with matter and the corresponding non-linear effects have been subject of lively research, both theoretical and experimental [1-6], especially in the infrared and visible photon energy regimes. Laser systems capable of producing high intensities also at photon energies in the (soft) X-ray regime open access to novel effects like non-linear Compton effects or simultaneous elastic and inelastic photon scattering, and allow multiphoton-ionisation experiments in a new domain [4-6]. However, experiments have so far relied on time-of-flight mass spectrometry or related methods and have been unable to analyse the reaction products with high accuracy, nor were they able to select or prepare products for further studies in a well-defined way.
We are currently setting up a Penning-trap-based experiment for multiphoton-ionisation of confined particles by highly intense and highly energetic laser light.
The particles (atomic or molecular ions) are confined in a cylindrical Penning trap with conical outer electrodes for access also with highly focused laser light and are subjected to the laser light in a controlled manner.
The reaction products are analysed in real-time by non-destructive methods. Such measurements are, for example, able to determine cross sections for multiphoton-ionisation in an energy- and intensity- regime so far not or not sufficiently examined. Additionally, the created electrons may be extracted from the trap and analysed externally. Hence, the reaction energetics may be reconstructed as completely as possible. The Penning trap setup is designed in a portable fashion, such that it can be attached to existing laser systems easily.
[1] G. Mainfray and G. Manus, “Multiphoton ionization of atoms”, Rep. Prog. Phys. 54 1333 (1991).
[2] D. A. Gobeli, J. J. Yang and M. A. El-Sayed, “Laser multiphoton ionization-dissociation mass spectrometry”, Chem. Rev. 85 (6) 529 (1985)
[3] K. W. D. Ledingham and R. P. Singhal, “High intensity laser mass spectrometry — a review “, International Journal of Mass Spectrometry and Ion Processes 163 149 (1997).
[4] H. Hasegawa et al., “Multiphoton ionization of He by using intense high-order harmonics in the soft-x-ray region”, Phys. Rev. A 71 023407 (2005).
[5] A. A. Sorokin, S. V. Bobashev, K. Tiedtke and M. Richter, „Multi-photon ionization of molecular nitrogen by femtosecond soft x-ray FEL pulses“, J. Phys. B: At. Mol. Opt. Phys. 39 L299 (2006).
[6] S. B. Popruzhenko, V. D. Mur, V. S. Popov and D. Bauer, “Multiphoton ionization of atoms and ions by high-intensity X-ray lasers”, Journal of Experimental and Theoretical Physics 108 947 (2009).
Job offers
collaboration:
Th. Stöhlker GSI / Helmholtz-Institut Jena
G.G. Paulus Universität Jena / Helmholtz-Institut Jena
W. Quint GSI / Universität Heidelberg
M. Vogel TU Darmstadt / GSI
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