Resonance-enhanced multiphoton ionization detection of vibrationally excited O₂

We report a rotationally resolved spectroscopic detection scheme for vibrationally excited molecular oxygen with high sensitivity. Two-color (2 + 1′) resonance-enhanced multiphoton ionization (REMPI) spectra of O₂ hot bands were recorded for the first time via the 3d π ( v ′ = 0 ) ← X 3 Σ g − (v″ = 1) Rydberg transitions. Spectroscopic constants and relative Franck-Condon factors were extracted and compared to simulations. This new access to quantum-state-resolved diagnostics of vibrationally excited O₂ promises to shed light on the physical and chemical dynamics of many processes.