Molecular alignment in degenerated dissociation channels in strong laser fields

In this work, we study strong-field molecular alignment in, for the first time, degenerated channels following the same charged states of molecules. By measuring the angular distribution of dissociation fragments from two degenerated N⁺ + N⁺ channels of N₂, we observe an opposite angular distribution development in these two channels, one expanding and one contracting, when the laser intensity increases. Our further study shows that the expanding channel comes from a nonsequential transition, while the contracting channel involves a sequential transition. We also study the time sequence of the sequential and nonsequential transitions and find that the opposite angular distribution development is due to the different degrees of molecular alignment in these two degenerated channels.