Knowledge Bank

Resonance enhanced multiphoton ionization studies in the 275-330 nm region reveal a large number of 2- and 3-photon transitions to previously unknown states. We have analyzed, in detail, four vibrational components of a rotationally resolved electronic transition at 8.2 eV. The vibrational frequency of $1870cm-1$ and a rotational constant of $1.68cm-1$ suggest that the upper state is the lowest Rydberg state (3s$\sigma$) of $O2$. The rotational structure is consistent with an electronic designation of $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Pi 0g-$ for this state.