TY - DATA T1 - Ion TOF spectra of Ne taken at the photon energy of 93.0 eV and the peak intensity of (a) 4 × 1015 W cm−2 and (b) 2 × 1013 W cm−2 PY - 2013/08/13 AU - R Guichard AU - M Richter AU - J-M Rost AU - U Saalmann AU - A A Sorokin AU - K Tiedtke UR - https://iop.figshare.com/articles/figure/_Ion_TOF_spectra_of_Ne_taken_at_the_photon_energy_of_93_0_eV_and_the_peak_intensity_of_a_4_b_b_10_su/1012461 DO - 10.6084/m9.figshare.1012461.v1 L4 - https://ndownloader.figshare.com/files/1480283 KW - cm KW - model KW - photon energies KW - Photon energy KW - ion charge states KW - rate equations KW - 30. Abstract KW - neon atoms KW - TOF regime KW - photoionization channels KW - ev KW - peak intensity KW - photoionization yields KW - ion intensities KW - intensity distribution KW - sequential photoionization KW - flash KW - laser beam KW - ionization yields KW - Atomic Physics KW - Molecular Physics N2 - Figure 2. Ion TOF spectra of Ne taken at the photon energy of 93.0 eV and the peak intensity of (a) 4 × 1015 W cm−2 and (b) 2 × 1013 W cm−2. In the TOF regime below 2.6 μs, the ion intensities were multiplied by a factor of 30. Abstract At the free-electron laser FLASH, multiple ionization of neon atoms was quantitatively investigated at photon energies of 93.0 and 90.5 eV. For ion charge states up to 6+, we compare the respective absolute photoionization yields with results from a minimal model and an elaborate description including standard sequential and direct photoionization channels. Both approaches are based on rate equations and take into account a Gaussian spatial intensity distribution of the laser beam. From the comparison we conclude that photoionization up to a charge of 5+ can be described by the minimal model which we interpret as sequential photoionization assisted by electron shake-up processes. For higher charges, the experimental ionization yields systematically exceed the elaborate rate-based prediction. ER -