The reaction of ground-state Y (a(2) D) atoms with ketene (H2CCO) was studied at two collision energies, 22.7 and 10.4 kcal/mol. At both collision energies, four competing processes were observed corresponding to formation of YCH2, YCCO, YCHCO (with elimination of CO, H-2, and H, respectively), and nonreactive scattering. The endoergicity of the YCHCO + H product channel was 10.5 +/- 2.0 kcal/mol, leading to D-0(Y-CHCO) = 93.4 +/- 2.0 kcal/mol. Product branching ratios measured at both collision energies show formation of YCH2 + CO to be dominant. The trend in branching ratios as a function of,collision energy, combined with center-of-mass distributions obtained through fits to the experimental data and analogies to the Y + H2CO system, allows a qualitative description of relevant features of the Y + H2CCO potential energy surface.