A matrix isolation study of the fluorescence of anthracene and anthracene-ammonia adducts in solid argon

The UV absorption and emission spectra of anthracene in an argon matrix were measured. Three major spectroscopic systems were observed, assignable to anthracene molecules occupying distinct sites. The origins of these systems were red-shifted with respect to the isolated molecule by 535,69 1 and 722 cm-‘. At 17 K all lines were well resolved, with about 8 cm-’ fwhm. Addition of a small amount of ammonia leads to the observation of three new band systems, red-shifted with respect to the previously mentioned ones. These observations are discussed in relation to recent studies of anthracene-argon and anthracene-ammonia clusters in supersonic jets.