MULTIPLE PHOTOIONIZATION OF NE IN THE K-SHELL IONIZATION REGION

Multiple photoionization of Ne in the K-shell ionization region (810-1340 eV) has been studied using a time-of-flight mass spectrometer. The singly charged ion Ne+ appears only at the 1s --> 3p excitation, except for production through direct L-shell ionization. The doubly charged ion Ne2+ shows the most intense yield above the 1s --> 3p excitation, and K-shell excited Rydberg states mainly turn into Ne2+ through Auger shake processes. The partial photoionization cross sections of Ne3+ and Ne4+ have maxima at about 130 eV and 230 eV above the is ionization threshold, respectively. These maxima are attributed to shake-off processes at the initial photoabsorption step. Double Auger processes following the 1s photoionization are estimated to happen at about 6% relative to normal Auger processes.