Doppler Broadening of the Annihilation Line in a Donor- and Acceptor-Intercalated Graphite Compound

Doppler broadening spectra of the annihilation line are measured for pure highly oriented pyrolytic graphite and for graphite intercalated by potassium (K) and iron chloride (FeCl3). It is shown that the annihilation peak is broader in intercalated samples than in pure graphite. In the classical case, the presence of large free volumes in the sample leads to a decrease in the annihilation line width. However, in intercalated graphite, the opposite behavior is observed, namely, an increase in the line width. Possible physical mechanisms responsible for this behavior are discussed.