Visualization of xenon double ionization as a function of the wavelength |
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| Bernd Witzel | |
| Université Laval, Quebec, CA | |
| Non-sequential (NS) atom double ionization processes driven by short pulse high intensity laser fields are mainly understood by theories that include the concept of an electron impact ionization process of the ion. At sufficient low laser intensities, where the impact energy is negligible, the ionization mechanism should be different. A proof of a possible contribution from the rescattering processes to double ionization can be done with a wavelength dependent measurement. The impact energy of the colliding electron can be varied within the laser peak intensity as well as with the frequency. We have studied the frequency dependence of single and double ionization of xenon in the multiphoton and tunnelling regime, by using a HE-TOPAS (traveling-wave optical parametric amplifier) system [1]. A portable mass spectrometer was used to measure the ionization yield of xenon single and double ionization in a wavelength regime between 500 nm and 2200 nm at laser intensities from 2 x 1013 W/cm2 to 1 x 1015 W/cm2. The 3D – plots (Xe+ - and Xe2+- ion yield versus Intensity and wavelength) obtained from our measurement will be compared with calculations from the PPT – theory [2]. Assuming that the single ionization of xenon is correctly predicted by this model [3], we can identify regimes of sequential and non-sequential ionization. In addition we will discuss the influence of the ionic transition 5s2 5p5 + m??? 5s 5p6 [4] on the double ionization process in the multiphoton as well as in the tunnelling regime. |