The h c (1 P 1) state of charmonium has been observed in the reaction ψ (2 S)→ π 0 h c→(γ γ)(γ η c) using 3.08× 10 6 ψ (2 S) decays recorded in the CLEO detector. Data have been analyzed both for the inclusive reaction, where the decay products of the η c are not identified, and for exclusive reactions, in which η c decays are reconstructed in seven hadronic decay channels. We find M (h c)= 3524.4±0.6±0.4 MeV which corresponds to a hyperfine splitting Δ M hf (1 P)≡⟨ M (3 P J)⟩− M (1 P 1)=+ 1.0±0.6±0.4 MeV, and B (ψ (2 S)→ π 0 h c)× B (h c→ γ η c)=(4.0±0.8±0.7)× 10− 4.
