  High-resolution photoemission is used to study the electronic structure of
the cuprate superconductor, Bi2212, as a function of hole doping and
temperature. A kink observed in the band dispersion in the nodal direction in
the superconducting state is associated with coupling to a resonant mode
observed in neutron scattering. From the measured real part of the self energy
it is possible to extract a coupling constant which is largest in the
underdoped regime, then decreasing continuously into the overdoped regime.
