Theoretical interpretation of multiphoton ionization of neon by soft-x-ray intense radiation

We present an attempt at the theoretical interpretation of recent experimental results on multiphoton ionization of neon by photons of energies 38.4 and 42.8 eV at the free electron laser facility [A. A. Sorokin , Phys. Rev. A 75, 051402(R) (2007)]. Although, given the photon energies, the intensities employed place the process within the regime of perturbation theory, effects such as the pulsed nature of the field and expansion of the interaction volume need to be and are taken into consideration. The values of some of the cross sections are obtained through scaling and given the semiquantitative nature of the calculations, overall reasonable agreement with the experimental data is found, although some issues pertaining to details remain as questions.