Precise and accurate measurements of strong-field photoionisation and a   transferrable laser intensity calibration standard
  Ionization of atoms and molecules in strong laser fields is a fundamental process in many fields of research, especially in the emerging field of attosecond science. So far, demonstrably accurate data have only been acquired for atomic hydrogen (H), a species that is accessible to few investigators. Here we present measurements of the ionization yield for argon, krypton, and xenon with percentlevel accuracy, calibrated using H, in a laser regime widely used in attosecond science. We derive a transferrable calibration standard for laser peak intensity, accurate to 1.3%, that is based on a simple reference curve. In addition, our measurements provide a much-needed benchmark for testing models of ionisation in noble-gas atoms, such as the widely employed single-active electron approximation. 
W.C. Wallace, O. Ghafur, C. Khurmi, Satya Sainadh U., J.E. Calvert,   D.E. Laban, M.G. Pullen, K. Bartschat, A.N. Grum-Grzhi...
physics.atom-ph