A theoretical explanation of the observed splittings among the P~states of
charmonium is given with the use of a nonsingular potential model for heavy
quarkonia. We also show that the recently observed mass difference between the
center of gravity of the 3PJ​ states and the 1P1​ state of ccˉ
does not provide a direct test of the color hyperfine interaction in heavy
quarkonia. Our theoretical value for the mass of the 1P1​ state is in
agreement with the experimental result, and its E1 transition width is
341.8~keV. The mass of the ηc′​ state is predicted to be 3622.3~MeV.Comment: 15 page REVTEX documen