Non-linear photoionization in the soft X-ray regime
نویسندگان
چکیده
At the new Free-electron LASer in Hamburg FLASH, we have studied photon-matter interaction by means of ion time-of-flight spectroscopy on gases in the soft X-ray regime. Emphasis was laid on the quantitative investigation of non-linear effects upon photoionization by the highly intense soft X-ray laser pulses. In the photon energy range from 38 to 93 eV, we have observed non-linearities due to space-charge effects, target depletion, and sequential and direct multi-photon ionization at irradiance levels of up to 10 W cm. The work is related to the development of photon diagnostic tools that are based on gas-phase photoionization for current and future X-ray laser facilities but might be of significance for any experiment at fourth generation light sources.
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