  The RENO experiment has analyzed about 500 live days of data to observe an
energy dependent disappearance of reactor $\overline{\nu}_e$ by comparison of
their prompt signal spectra measured in two identical near and far detectors.
In the period between August 2011 and January 2013, the far (near) detector
observed 31541 (290775) electron antineutrino candidate events with a
background fraction of 4.9\% (2.8\%). The measured prompt spectra show an
excess of reactor $\overline{\nu}_e$ around 5 MeV relative to the prediction
from a most commonly used model. A clear energy and baseline dependent
disappearance of reactor $\overline{\nu}_e$ is observed in the deficit of the
observed number of $\overline{\nu}_e$. Based on the measured far-to-near ratio
of prompt spectra, we obtain $\sin^2 2 \theta_{13} = 0.082 \pm 0.009({\rm
stat.}) \pm 0.006({\rm syst.})$ and $|\Delta m_{ee}^2|
=[2.62_{-0.23}^{+0.21}({\rm stat.}) _{-0.13}^{+0.12}({\rm syst.})]\times
10^{-3}$~eV$^2$.
