Energy partitioning in the 203-205 nm photodissociation of N2O was studied by velocity map ion imaging of O(D-1(2)) and (2+1) resonance-enhanced multiphoton ionization (REMPI) of N-2 (X(1)Sigma(g)(+)) via the a"(1Sigma(g)(+)) state. The observed translational energy distribution of O atoms exhibited a discrete structure due to quantized rotational energies of the counterpart N-2 fragments. The maximum of the N-2 rotational distribution has shifted from J = 72 to 74 in changing the photodissociation wavelength from 205.5 to 203.8 nm. Comparison of the translational energy distribution of O(D-1(2)) With the REMPI spectrum of N-2 (X(1)Sigma(g)(+)) revealed that the REMPI intensities of N-2 via particular rotational levels in the a" state were specifically reduced. These rotational levels exhibited energy shifts due to perturbation, indicating that the REMPI efficiency is reduced by the interactions between the a" state and other valence electronic state(s).