Zeeman Effect in the Electronic Spectrum of Solid CS2

The lowest-energy 3A2←1Σg+ singlet-triplet transition of CS2 has been studied in the CS2 crystal at 4.2°K. The spectrum consists mainly of progressions in the bending mode ν2'. The following values for the upper state frequencies have been obtained (v1'=677 cm–1, ν2'=309 cm–1) and the unobserved B2 electronic origin has been calculated to be at 24739 cm–1. Zeeman studies of the 3676-Å band system have been used to assign a very weak component of a vibronic band of this system as a crystal field induced transition to the (A1, B1) pair of spin sublevels of the triplet state 3A2. The zero field splitting (ZFS) parameter of 36±1 cm–1 thus obtained for the vibronic state is comparable with the one earlier calculated from Zeeman line broadening experiments in the gas phase earlier done on comparable vibronic bands. The large value of the ZFS parameter can be explained if it is assumed that the 3A2 and 3B2 states are quite nearby.