When pure anthracene is melted under a pure nitrogen atmosphere in
the presence of an alkali
metal, the metal dissolves forming a blue-green melt which exhibits an electron
spin resonance (e.s.r.) signal. The polycrystalline samples of the solid system
(MAn) obtained by cooling the melt also exhibit e.s.r, signals but with a line-width greater than that seen
in the melt. The Lorentzian
line-shapes in the solid and the melt indicate that the electrons producing the
signals are either delocalized, or clustered and undergoing exchange
interaction. The following features are
discussed: the lack of hyperfine structure in the melt except for a special
case; the Curie dependence of the susceptibility; the dependence of the
g-values on the alkali metal; the shifts of the g-values on melting the
samples; the behaviour of the line-width with respect to deuteration
of anthraoene and with respect to the different
alkali metals; and the dependence of the spin-lattice relaxation time on the
alkali metal and on whether the sample was solid or molten. The features
indicate that the electrons behave as simple doublets, are clustered with the
alkali-metal complex in the solid and undergo exchange interaction, produce
motional narrowing of lines in the melt, and produce a line-width mainly
dependent on the alkali metal ions in the solid and to a lesser extent in the
melt.
