The double ionization of xenon in the multiphoton regime has been studied at two wavelengths (0.77 and $0.79\mu \mathrm{m}$) using an electron-ion coincidence technique and an intensity binned ion ratio method. Sharp resonant structures in the electron energy distribution correlated with the doubly charged ion, as well as a wavelength dependence of the ${\mathrm{Xe}}^{2+}/{\mathrm{Xe}}^{+}$ ratio provides new insights. A mechanism involving the shelving of population in Rydberg states followed by excitation of a core electron is proposed.

• Received 3 September 2003

DOI:https://doi.org/10.1103/PhysRevLett.92.203001