J/psi and psi(2S) Radiative Transitions to eta_{c}.

Using 2.45x10{sup 7} {psi}(2S) decays collected with the CLEO-c detector at the Cornell Electron Storage Ring we present the most precise measurements of magnetic dipole transitions in the charmonium system. We measure B({psi}(2S){yields}{gamma}{eta}{sub c})=(4.32{+-}0.16{+-}0.60)x10{sup -3}, B(J/{psi}{yields}{gamma}{eta}{sub c})/B({psi}(2S){yields}{gamma}{eta}{sub c})=4.59{+-}0.23{+-}0.64, and B(J/{psi}{yields}{gamma}{eta}{sub c})=(1.98{+-}0.09{+-}0.30)%. We observe a distortion in the {eta}{sub c} line shape due to the photon-energy dependence of the magnetic dipole transition rate. We find that measurements of the {eta}{sub c} mass are sensitive to the line shape, suggesting an explanation for the discrepancy between measurements of the {eta}{sub c} mass in radiative transitions and other production mechanisms.