  The final stage of gas giant formation involves accreting gas from the parent
protoplanetary disk. In general, the infalling gas likely approaches a
free-fall velocity, creating an accretion shock, leading to strong shock
heating and radiation. We investigate the kinematics and energetics of such
accretion shocks using 1D radiation hydrodynamic simulations. Our simulations
feature the first self-consistent treatment of hydrogen dissociation and
ionization, radiation transport, and realistic grey opacity. By exploring a
broad range of giant planet masses (0.1-3 M$_{J}$) and accretion rates
($10^{-3}$-$10^{-2}$M$_{\oplus}\cdot\rm{yr}^{-1}$), we focus on global shock
efficiency and the final entropy of the accreted gas. We find that radiation
from the accretion shock can fully disassociate the molecular hydrogen of the
incoming gas when the shock luminosity is above a critical luminosity.
Meanwhile, the post-shock entropy generally fall into "cold"
($<12k_{\rm{B}}/m_{\rm H}$) and "hot" ($>16k_{\rm{B}}/m_{\rm H}$) groups which
depends on the extent of the endothermic process of $\rm{H}_2$ dissociation.
While 2D or 3D simulations are needed for more realistic understandings of the
accretion process, this distinction likely carries over and sheds light on the
interpretation of young direct imaging planets.
