  Massless perturbative QCD forbids, at leading order, the exclusive
annihilation of proton-antiproton into some charmonium states, which, however,
have been observed in the $p\bar p$ channel, indicating the significance of
higher order and non perturbative effects in the few GeV energy region. The
most well known cases are those of the $^1S_0$ ($\eta_c$) and the $^1P_1$. The
case of the $^1D_2$ is considered here and a way of detecting such a state
through its typical angular distribution in the radiative decay $^1D_2 \to$
$^1P_1 \gamma$ is suggested. Estimates of the branching ratio $BR(^1D_2 \to
p\bar p)$, as given by a quark-diquark model of the nucleon, mass corrections
and an instanton induced process are presented.
