Investigating strong-field induced rotational coherences in the cationic states of oxygen using UV pulses and high-resolution FFT spectroscopy

We investigate the bound wave packet populated by an intense 800-nm pulse in low-lying cationic states of oxygen. This wave packet is probed using dissociation by a UV pulse. The delay-dependent momentum distribution of O⁺ is Fourier transformed to obtain kinetic-energy-dependent and rotational-state-resolved quantum beat spectra. The Fourier spectrum shows dominant signature of wave packets in b⁴Σ_{g}^{_} and the X²Π_g states. The similarity in appearance of the b⁴Σ_{g}^{_} state quantum beat spectra compared to the case of a weak 800 nm probe confirms the resonant coupling between b⁴Σ_{g}^{_} and a⁴Π_g induced by the 800 nm pump. The dominance of the X²Π_g(v=3) state, on the other hand, shows the importance of resonant coupling in the UV probe pulse. Rotational coherence in the X²Π_g state also shows correlation between rotational and electronic dynamics via spin-orbit coupling.