Vibronic coupling in triatomic radicals and its spectroscopic implications: two and three state interactions in doublets and triplets

The breakdown of Born-Oppenheimer approximations always represents a source of unexpected effects in the rovibronic spectra of molecules. For triatomic radicals, the problem may be handled almost exactly by means of the variational methods implemented into the RVIB3 code, including all sources of angular momentum present in the system. Recent developments of RVIB3, including - (three states) interactions1,4, intensities calculations2 and handling of triplet multiplicity3 are reviewed, with emphasis to molecular applications. The methods are applied to the discussion and assignment of the recently published5 high resolution ZEKE photoelectron spectrum of O3 .