  Using high energy resolution angle resolved photoemission spectroscopy, we
have resolved the bilayer splitting effect in a wide range of dopings of the
bilayer cuprate $Bi_{2}Sr_{2}CaCu_{2}O_{8+\delta}$. This bilayer splitting is
due to a nonvanishing intracell coupling $t_{\perp}$, and contrary to
expectations, it is not reduced in the underdoped materials. This has
implications for understanding the increased c-axis confinement in underdoped
materials.
