SINGLET TRIPLET SPECTRA OF THE TETRAPHENYL DERIVATIVES OF GROUP IV ELEMENTS.

Author Institution: Laboratory for Research on Molecular Structure, University of PennsylvaniaThe polarized absorption spectra of single crystals of tetraphenyl lead, tin, germanium, and silicon have been examined at $4.2^{\circ}K$. The $0-0$ bands were split into several components separated by about $3 cm^{-1}$, and this splitting has been assigned as arising from intra-molecular exchange splitting. The energy of the $0-0$ band was found to increase as the size of the central atom increased. High field Zeeman experiments indicate that two spin-orbit routes predominate. Preliminary examination of the phosphorescence indicates that the emission may originate from two of the intramolecular exchange states