Inner-electron ionization of Sr 5s16l states

We have measured the probability of inner-electron ionization (IEI) of Sr 5s16l atoms when exposed to intense 230-fs laser pulses. We find that the probability of IEI rises sharply at l=5 and is approximately equal to one for l>5. For l=5 the classical inner-turning point is at 15a0, far greater than the size of the Sr+ ionic core, ruling out core penetration as the factor governing inner-electron ionization. For the Sr 5p1/216l states of l>5 the autoionization lifetime, which is due to the electrostatic interaction between two-valence electrons, is greater than the Kepler orbit time. These comparisons suggest that both inner-electron ionization and autoionization are governed by long-range electrostatic interactions