Electronic Zeeman Measurements on 1,4-Dibromonaphthalene

A summary of interpretive methods regarding high-field electronic Zeeman measurements is presented. The equations calculated for two active spin substates (zero field) of the lowest triplet state, are applied to 1,4-dibromonaphthalene crystal spectra. The Zeeman spectra of the electronic and vibronic origins of the lowest triplet state have different polarization, but they have very similar Zeeman effects indicating similar spin-substate activity. The complete analysis enables us to show that the lowest triplet state is of species 3B2 which correlates with 3B2u in D2h. The vibronic origins are shown to arise by spin-orbit coupling with singlet states that are vibronically mixed with other singlet states. Certain crystal-field effects are apparent in the spectra and those are discussed in relation to two suggested types of mixing; namely, intermolecular spin-orbit coupling, and intermolecular exchange coupling.