Visible chemiluminescence in the 4300-6600 Å region was observed from the Ca+N2O and Ca+O3 reactions in argon matrix. The broad bands at 6066 and 6246 Å were ascribed to the d 3Δ (or D 1Δ)→a 3Π and the D 1Δ→A′ 1Π transitions of CaO, respectively. A weaker band at 6416 Å (15 586 cm-1) was assigned as emission from the previously unobserved c 3∑+ state to the a 3Π state of CaO. Emission due to Ca atoms in the 1P(4s4p)→1S(4s2) and the 3P(4s4p)→1S(4s2) transitions was also observed as sharp peaks at 4231 and 6575 Å, respectively. The atomic emitters were excited by energy transfer from CaO*, most probably from the D, d, and c states. The Ca(3P) also receives population via fast relaxation from the 1P state.