Terahertz spectroscopy of oxygen, O2, in its 3Σ−g and 1Δ electronic states: THz Spectroscopy of O2

High precision rotational spectra of isotopic oxygen O2 (with O16 or O18) in its Σg−3 electronic ground state have been measured in selected frequency regions between 0.4 and 2.0 THz. The main isotopic species, O216, was also investigated in its first excited electronic state Δ1. The new data, analyzed together with previous measurements, yielded improved spectroscopic parameters.