Effect of an External Heavy Atom on the Photochemistry of Monofluorobenzene Vapor. II

The effect of added Xe on the singlet and triplet yields of monofluorobenzene vapor excited at 2670, 2520, and 2470 Å has been reinvestigated. The fluorescent yields, and hence the singlet yields, were monitored directly while triplet yields were determined by both the sensitized emission of biacetyl technique and the isomerization of olefins technique. The data obtained confirm that Xe enhances intersystem crossing in monofluorobenzene (1). However, contrary to results previously published from this laboratory (1), Xe does not quench the triplet state of biacetyl.