Efficient production of metastable fragments around the 1s ionization threshold in N₂

Metastable formation has been investigated in the inner-shell region of N₂. Enhanced N* formation has been observed around the 1s threshold, and is shown to result from dissociation of high N₂ ⁺* Rydberg states. These N₂ ⁺* states are populated by spectator Auger decay from core-excited states, as well as by the recapture of slow photoelectrons into the Rydberg orbitals. The present measurement demonstrates that the metastable observation is a new and sensitive tool to study the decay dynamics of core-excited states and the photoelectron recapture due to post-collision interaction.