Rydberg–valence interactions in the Πg states of O2

Abstract
Multiphoton ionization spectroscopy is used to characterize the (3sσ) 3Πg Rydberg state of O2. It is found that the 3Πg Rydberg state is very diffuse and has rotationally resolved structure for the v’=2 level only. The FWHM of rotational lines for both the (3sσ) 3,1Πg states is greater than the excitation bandwidth, indicating strong radiationless decay of the two states. Interactions with the nearby 3Πg and 1Πg valence states are invoked to explain the observed behavior.