Potential Energy Curves of Molecular Nitrogen for Singly and Doubly Ionized States with Core and Valence Holes

Our manuscript, presents the computation of potential energy curves of all possible singly and doubly ionized states of molecular nitrogen. Accurate representation of the potential energy curves of ionized states of N₂ is essential to explicitly treat coupled electron-nuclear dynamics. In this work, we compute the potential energy curves of the valence as well as the core and inner valence singly and doubly ionized states of N₂. These curves pave way to study the interplay between photoionization and Auger spectra when molecular nitrogen interacts with free electron lasers.

Computation of inner valence or core ionized potential energy curve is not trivial due to the well-known problem of variational collapse of the wavefunction to the lowest energy state. We circumvent this problem by implementing a two-step optimization scheme within the multi-configurational self-consistent field approach. Such a two-step optimization scheme has been previously implemented to compute potential energy curves of core ionized states of di-atomic molecules with one hole. Herein, we show the general applicability of this two-step optimization method by computing potential energy curves of both singly and doubly ionized states of N₂ with valence and core holes. Calculation of potential energy curves for core ionized polyatomic systems are scarce. Moreover, our approach is system independent and can be easily extended to calculate multiple-core ionized states. To the best of our knowledge, this is the first calculation of potential energy curves for doubly ionized states of a diatomic molecule with two core (or inner valence) holes.