Soft x-ray driven femtosecond dynamics of ionic Rydberg states in N2*

We present the first direct observation of molecular dynamics initiated by a EUV pulse. A novel EUV pump- IR probe technique is used to observe these dynamics. The EUV pulse, with h(nu) = 42 eV, launches molecular nitrogen into highly-excited (N2)2+ core Rydberg states,~ the dynamics of which are previously unexplored. We use a time-delayed infrared pulse to promote the wavepacket from the Rydberg state to a dissociative (N2)2+ state via multiphoton ionization. The kinetic energy release of the N+/N+ channel is obtained as function of time delay. Having identified the final (N2)2+ state, we extract the potential energy curve corresponding to the evolving Rydberg state. The Rydberg state initially behaves the same as the (N2)2+ state. As the internuclear distance increases, we observe a fast decrease in the kinetic energy release on the time scale of 100 fs, corresponding to a transition from the molecular Rydberg state to N+ and N fragments.