OPTICAL SPECTROSCOPIC STUDY OF TETRACENE GUEST SITE CONFIGURATIONS INPERDEUTERATED AND PARTIALLY DEUTERATED P-TERPHENYL HOST CRYSTALS

The nature of the stable guest sites, O-1 and O-2, and the conformatio nal relaxations in the host cage of the metastable sites, O-3 and O-4, of tetracene in partially deuterated and perdeuterated p-terphenyl cr ystals are investigated using stationary optical spectroscopy, Deutera tion of the p-terphenyl host matrix leads to blue-shift the electronic origins of the guest spectra and a decrease of the splitting between the spectral lines of the O-1 and O-2 sites. The phonon sidebands in t he excitation spectra of the metastable O-3 and O-4 sites in perdeuter ated p-terphenyl were found to have a significantly smaller width as c ompared to that of the perprotonated host. This difference is shown to reflect the relatively smaller conformational changes of the perdeute rated host molecules surrounding the guests in the O-3 and O-4 sites.