Absolute photoionization cross-section measurements of the excited4Dand5Sstates of sodium

Abstract
We have measured the absolute cross section for photoionization of the 4D and 5S excited states of sodium for 1.06 μm radiation. The method of measurement is based on saturation of ionization probability at high intensity of the ionizing radiation. The measured cross sections for ionization of unaligned atoms are 15.2±1.7 Mb for the 4D state and 1.49±0.13 Mb for the 5S state, both in excellent agreement with calculated values.