Relaxation of the 4d→5presonance in atomic iodine

Iodine atoms, produced by laser-induced dissociation of molecular iodine, have been photoexcited with synchrotron radiation in the region of the 4d-shell excitation. A strong resonance is observed below the 4d ionization threshold, which is assigned to the 4d→5p${(}^2$ ${\mathit{D}}_{5/2}$) transition. Photoelectron spectra reveal that the main decay of such an excited state is through direct autoionization into outer shells, especially into singlet states. Above the 5${\mathit{s}}^{\mathrm{-}1}$ threshold, numerous lines are observed, which cannot be understood in a single-particle framework. Indeed, ab initio calculations point out that the 5${\mathit{s}}^{\mathrm{-}1}$ configuration is strongly mixed with the 5${\mathit{p}}^3$ ${(}^2$P)5d and 5${\mathit{p}}^3$ ${(}^2$D)5d configurations, so that observed lines cannot be separated into main and satellite lines. Moreover, strong dynamic correlation effects are observed via a strong variation of the Auger decay rate with the kinetic energy of the Auger electron.