  We simulate the nonequilibrium steady state \textit{cis-trans}
photoisomerization of retinal chromophore in rhodopsin based on a
two-state-two-mode model coupled to a thermal environment. By analyzing the
systematic trends within an inhomogeneously broadened ensemble of systems, we
find that the steady state reaction quantum yield (QY) correlates strongly with
the excess energy above the crossing point of the system, in agreement with the
prediction of the short time dynamical wavepacket picture. However, the
nontrivial dependence of the QY on the system-environment interaction indicates
that a pure dynamical picture is insufficient and that environment-induced
partial internal energy redistribution takes place before the reaction
concludes. These results imply that a proper treatment of the
photoisomerization reaction, particularly its high QY, must account for the
redistribution and dissipation of energy beyond the dynamical wavepacket motion
that is typically employed in the literature and that is appropriate only in
the transient regime.
