The effect of particle size
of substrate and tritium gas pressure on the efficiency of Wilzbach tritiation
of crystalline polycyclic hydrocarbons has been investigated.
The hydrocarbons studied included
naphthalene, biphenyl, phenanthrene, chrysene, pyrene, m- and p-terphenyls, and
acridine. No simple relationship between ionization potential and tritium
incorporation was observed. The effect of radical scavengers such as nitric
oxide and moderators such as helium on the labelling process have been examined.
Tritium incorporation in a polycyclic
hydrocarbon is enhanced lf gas exposure occurs in the presence of benzoic acid.
The results are discussed in terms of current theories proposed for tritium
labelling based on gas-phase studies. In the condensed phase present data show
that radical processes are important in Wilzbach labelling. This has been
confirmed by a preliminary e.s.r. examination of naphthalene and anthracene in
the presence of tritium gas.
